Yeah ditto what everyone has said so far.
We had a female betta in our 28 community tank. She was a very sociable fish. She loved swimming and hanging out with the cories, and when we put the Blue Ram into the tank, they hung out together.
Now that's not to say that will happen to all fish though, it depends on their personalities.
But blahblahblah... go with peaceful fish and you should be ok.
Some rasboras would be great. The harlequin variety are very pretty and peaceful. Just make sure to get about 6 of them though since they're schooling fish.
Danios would be ok too, but people have said theirs are nippy. I've never experienced fin nipping when we had danios. They would chase eachother, but other than that, no fin nipping every occured between them or them and the other fish. They're very active fish and come in a small varity of colors. There are ones that are called glolight? I think that are genetically altered to have bright neon colors. Those are ok to get as well since they're not dyed.
I would actually rethink getting more female bettas. You can't predict what sort of personalities they will have and one or more of them might be the type that just does NOT want to be with other fish and will attack the other girls so will have to be seperated.