Three budgies, one left out?!

As the title says, we have three budgies, two females and a male. One of the females and the male are very bonded and tend to leave the other female out. She tries to get involved but they don’t let her. She doesn’t seem unhappy but she’s very destructive / messy, could she be lonely? Wondering if it would be best to get a fourth budgie, maybe another male - is this a good idea?

Problem is I don’t want to add another budgie into the group and the currents ones not get on with it!

Advice much appreciated please ☺️