friends?

I'm the first in my girl trio to have a boyfriend I've had one before and had a couple "flings". I'm newly 18, and the guy I'm seeing is serious than the others. Ever since, my 2 best friends don't talk to me anymore. They never snap/msg me back, or hold a conversation. They don't like my statuses or instagram posts anymore (I know it's trivial) I haven't abandoned them. I don't understand? Opinions?