I would use any any of these words "absolutely ridiculous " for example

That is my suggestion. I hope you find this helpful.

Context

silly humour

The context provided is fragmentary. We don't know which behavior triggered the line

ترى يا بنات هذه مو أنوثة هذا دلع ماسخ

We know from يا بنات that it was addressed to young females. We also know from هذه مو أنوثة that the behavior being addressed is the kind of behavior that involves an aspect of femininity that requires a more mature attitude and conduct. We can tell that the speaker disapproves of the behavior on the grounds that it is of poor taste (ماسخ) and that it shows lack of self-discipline and lack of mature self-respect (دلع). We don't know much else. Did the behavior involve risqué attire, excessive makeup, sultry perfume, choice of words, topic of conversation, bodily posture, suggestive walking, indecent exchange of communication, or something else?

Without additional information, I am guided solely by the text of the fragment, which is limited. Let us take it piece by piece.

1. دلع: This is a modern slang word used in most regional dialects of Arabic. Slang words tend to be semantically loose and stretchy. The meaning is not boxed in by a tradition of standard usage in normative literature, so people feel free to stretch the word to fit a relatively wide variety of situations, the way a balloon artist stretches a balloon to make a giraffe or a rabbit.

The word carries a cluster of related significations, most of which revolve around behavior that might be tolerated in a child, within limits, but is considered unbecoming when observed in an adult or a maturing young person, except within the bounds of an intimate relationship.

Doting parents enjoy letting their children express themselves freely in order to allow them to grow uninhibited. They also enjoy watching their children make fools of themselves as they learn how to talk, eat, dress themselves, make art, and play sports. The expectation is that the children will eventually outgrow their childish silliness and assimilate adult behavior and the adult attitude of responsibility. Children, however, are in no hurry to grow up when they sense that grown-up responsibility is no fun, so they maintain childish behavior when it is no longer acceptable. That is when we begin to call it دلع. It is not cute anymore. Silliness becomes naughtiness.

Why do children behave this way? (1) They expect unconditional approval. They are shocked to find out that certain behavior is simply unacceptable. (2) They expect unconditional protection from consequences of their naughtiness. They are horrified to find out that their parents will not be able or even willing to rescue them from every scrape they get into by their own folly. (3) They expect to have all their desires fulfilled. They throw dramatic tantrums when they find out that their privileges, no matter how extensive, are not limitless. (4) They believe that parents and other adults are more generous with their love towards little, helpless, cute, sweet children. With this belief, they engage in emotionally manipulative behavior to milk more love out of their parents or other adults by pressing certain buttons that are hard to resist. Any of these behaviors can be called دلع.

How do you translate this to English or any other language? Generally, it will depends on the specific type of behavior. In the absence of a clear description of the behavior, a good translation should attempt to capture the general attributes: childishness or immaturity, disregard for social norms, lack of care for consequences, and inappropriate emotional manipulation of others (In the text under consideration, I suspect that these girls may have engaged in emotionally manipulative or provocative behavior).

Girlishness is the quality of being like a girl. When applied to males, it indicates sissiness. When applied to females, it indicates behavior that is unbecoming of a lady. In the Arabic text, the girls seem to behave in a manner that they think will bring out their feminine attributes, but they are being counseled that this behavior fails to accomplish this objective. Instead, it shows a degree of immaturity that would eclipse their full femininity. They are being girlish. The fullness of their feminine grandeur is diminished by immature behavior.

Silliness is the kind of behavior that does not show maturity and does not command respect.

I would go with either one as a translation of دلع.

2. ماسخ: This term is borrowed from the culinary arts. Food is supposed to appeal to the sense of taste by being sweet, salty, tart, or bitter. Some foods do not stimulate the sense of taste intensely enough, so we add flavorful enhancers, like honey, salt, lemon juice, herbs, spices, or extracts, or we subject the food to cooking techniques that bring out more flavor, like roasting. When we fail to do these things, food falls flat. In Arabic, we call it ماسخ. In English, we describe it as bland, insipid, or tasteless.

Both in Arabic and in English, these words can also be used to describe behavior that is unappealing. When we describe behavior as ماسخ, we mean that it is the kind of behavior that one should not be proud of. It has little value or even negative value. In English, we describe such behavior as “in poor taste” or simply “tasteless.” Vulgar language is often described as “off-taste” because it strikes us like food that has not only lost its original flavor, but has begun to acquire the taste of spoiled food.

The author of the text you are translating clearly wanted to use the taste metaphor. If you want to be faithful to the text, you must preserve the metaphor, especially since it is used in English in exactly the same way.

Again, if we knew what the behavior in question was, we would be able to fine-tune the translation more accurately.

Too much sassiness


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Note added at 1 day 18 mins (2020-06-13 10:25:42 GMT)
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This is not femininity, this is sassiness

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Note added at 1 day 18 mins (2020-06-13 10:25:59 GMT)
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هذه مو أنوثة هذا دلع ماسخ