Yea they can get egg bound even when totally isolated. There are ways to save them, though. Domesticated bettas mate by having the male wrap around the female and squeezing her, pushing her eggs out. It temporarily paralyzes her to prevent her from eating all the eggs, which she is accustomed to doing since they are not fertilized. Basically if a girl gets egg bound you have to apply gentle pressure to her to mimic the male's role, otherwise she will swell up and die.
As for food, I'm sure you know not to over feed them but whatever feeding schedule you give them you should keep to as well.
I run my tanks with marimos and ghost shrimp to keep it extra clean, if you're looking for maintenance ideas. Your betta may or may not bully the shrimp.