Huh? That doesn't sound right at all.
There's no definite (or indefinite) articles in Russian. So, the same Russian phrase might mean "Is this the girl" or "Is this a girl".
та simply means that, and is clearly much more emphatic. Someone please correct me if I've said something incorrect here.
It's true that Russian doesn't have articles, but that doesn't mean you can just assume that any article applies to any given translation. "Это девочка?" can only mean "is this a girl?", i.e. "девочка" is a category to which "это" belongs.
In fact, it's impossible to say "Is this the girl?" in Russian exactly the same way as it is an English (hence a lot of Russians having trouble understanding the purpose of the "the" ) so you have to substitute it with the closest equivalent, which is "это та девочка?" using "that" instead of "the" , so ns_shadow's answer was correct.
According to Yandex Translate, "This girl?" translates into "Эта девочка?" Notice it's no longer Это, but Эта. If anyone knows that I am wrong, please correct me. https://translate.yandex.com/?text=%D0%AD%D1%82%D0%B0%20%D0%B4%D0%B5%D0%B2%D0%BE%D1%87%D0%BA%D0%B0%3F%20%D0%AD%D1%82%D0%BE%20%D0%B4%D0%B5%D0%B2%D0%BE%D1%87%D0%BA%D0%B0%3F&lang=ru-en
It is about how you put stress on the words. You can do the same in English. For example, "got the keys" can mean, "I've got the keys". Whereas by putting stress on the 'o' and going up at the end of the sentence, as in "gOt the keys?" we can ask a question, "have you got the keys?". In the case of это, stress the э.
Can "It is a girl?" work here? I get that in English its a little clunky, but, imagine you were expecting a boy and the doctors told you you were having a boy and you saw the weewee on the ultrasound and picked out the name Carter Joseph and you push and push and push and... "It's a girl?"