Depending on your Betta you have many options. I like the Endlers I have in my 5g at the moment, they're chill, small fish who don't go after Ori and his big fins and they get out of his way during meal time. The Rams in the 10g really like the other fish so far. I did hear that golden rams can be a bit more aggressive for some though. These guys are EBRs.
A lot of people love Tetras and Rasboras, they will typically leave your Betta alone. But if she doesn't like company then.. they will be targets. :P