"Your girl plays."
Translation:Dein Mädchen spielt.
Yes, it can.
"Ihr" translates to a multitude of words in English:
So, the sentence "Ihr Mädchen spielt" translates to one of the following:
"Your girl plays,"
"Her girl plays" or
"Their girl plays."
Actually there is a fourth variant possible that this sentence could translate to: "You girls play," which could either be meant as an observation or an invitation/request.
Though, the observation would probably be said as "You girls are playing" to express the immediacy of the action.
So, whereas in the first three translations the speaker is addressing one or more than one person and talks about his, her or their girls, in the fourth variant the speaker addresses the girls themselves as in "Hey, you girls are playing" (observation) or "Hey, you girls play now" (invitation).
I think what you mean is euer Mädchen spielt.
Ihr Mädchen spielt corresponds to the formal you, but you are correct in a way because the formal you is singular and plural, so it wouldn't matter if you address a single parent or multiple. One thing to note is that the Ihr has to be capitalized.