Even if I take out the word "girls" from this sentence, does the meaning stay the same?
Yes. The meaning of the sentence would not be affected by the loss of "girls". Since "you" is both singular and plural, it can function here to indicate all three girls. However, the use of "girls" adds emphasis and is a common practice in spoken English. You will often hear native speakers add in something after "you" in this way, "you guys", "you kids", "you people" etc, even though "you" on its own would be fine. This is because we want to emphasize that we are speaking to more than one person. This is because "you" is both singular and plural, and there is no change in pronunciation or intonation to indicate a difference. Ex: What did you do this weekend? Ex: What did you guys do this weekend? Ex: You are being really noisy. Ex: You kids are being really noisy.