She'll be fine in the 5 gall - they're not always good in community tanks, other fish can be stressful. Females in particular can be quite shy and easily stressed. Yes, sometimes it works, but if the alternative of a solitary home is available it's always preferable. They're not social fish really, she won't be lonely. You could maybe add some amano shrimp - big enough not to get eaten and won't breed.
For decor try to get a small broad leafed plant for her to rest on, and something she can hide in too. Coconut cave maybe.
Her fins should grow back in time in good water, though they might not be perfect.
Temperature wise aim for about 26c.