How many do you have? Female bettas can be put together, but if one of
them is already in the big bowl you want to put them all in, then take
it out, rearrange the rocks and plants then put them all back in, so
any established territory is destroyed.

Female bettas can be aggressive, just like the males, so people
recommend that if you are going to have a few of them, you should have
at least 6, so they can form a pecking order. Don't get 2, or else
you'll find one becomes the dominant one and the other becomes it's
beeyach and gets constantly picked on til it dies. Occasionally they
will fight and you might get some nipped fins sometimes.

Not sure if your bowl is big enough for 6, but I'd put some plants in -
the female bettas I had tended to swim around the top of the tank -
looked strange because I had 6 of them in a 30gal tank and it used to
really annoy me that they wouldn't make use of the entire tank! So the
point I'm making there is that you might like to have some floating
plants.

Good luck!