They pretty much said in the promotional material that Megan learnt about Earth culture purely from watching tons of TV, which is both where she got that annoying "HELLO, Megan!" catchphrase from (they had canned laughter to it in the show she saw, so presumably she adopted it thinking that it'd continue to be funny) and her idea of what human girls do are similarly effected by this.

Hence her baking cookies for everything and acting extremely stereotypically girly, which could be taken as her acting that way because the TV shows she saw were very old fashioned and had a poor portrayal of women in it (causing Megan to unintentionally keep the ideas in circulation) because of this, OR she copied it because "that's how girls act" but she genuinely likes baking and the like.

Nothing wrong with that, not everyone is Artemis or how Babs was in the DCAU, BUUUTTTTT... the kinda meta way of protraying Megan was kind of lost on a lot of people.

The idea of a female character acting kind of one dimensional and stereotypically "girly" because the fictional depictions of woman acted as such and, presumably her culture doesn't have the same entertainment values as us,would presumably be a bit of a complicated thought process to follow.

She has got better as the show's gone on now, she acts more like a person in the newer episodes as opposed to a person playing a "character", if that makes sense.