21M, no success as of yet

Whenever I'm at the bar or a party, girls are always in the middle of a conversation with a guy or other girls. I feel like if I approach them there, I'm intruding on their conversation and I don't want to do that. I don't know, I guess my mother raised me not to interrupt people when they're talking. However, I so rarely see girls by themselves, and even if they are and I start a conversation with one, she'll migrate back to her friends in a few minutes. I'm not sure if it's socially acceptable to just invite myself into a circle and start talking, especially a group of girls. How do I navigate this situation? It is a significant portion of my approach anxiety at night.