I had female bettas with obvious oviposter that ended up looking pretty much like male plakats and some of them made bubblenests. They lived together peacefully for close to 2 years, then they got old and cranky and I had to separate some of them before they eventually passed.
I know of one female betta that made a bubblenest in tank on her own, dropped eggs and put them in the nest by herself as well. Obviously not fertilised so nothing happened and she ate them after a bit but still females do make bubblenests sometimes.