I have a female Betta and female African Dwarf Frog (ADF) that live together in a 10-gallon tank with sand substrate. Each ADF requires at least 2 gallons, so you probably won't want to keep more than one with your Betta in a 5-gallon tank.
Like Bettas, ADFs thrive on Bloodworms, frozen or live. But, they are very slow to find their food. I feed the Betta first. Then I feed the ADF with an eyedropper. Sometimes she even holds it with her front flippers like a baby bottle.
ADFs also like things they can hide under. I added a small, upside down, clay-pot saucer, with an opening cut in the side. There's also a piece of driftwood she can crawl under.
The ADF is very active and very sweet. She greets me with bubble kisses every morning.