Might go both ways but I would personally throw in a couple of more females (if it were a big tank). I have 1 male and 3 females in my betta chillout tank (30G planted) and they all get along nicely. When breeding and alone they change their behaviour. My blue bigger female gets really aggresive when alone as well. But when dropping her in with her tank friends it just switches and they are all happy. Might be some occasional flaring etc but never any fighting. My tank is bigger and I do not think any fish should need to live permanently in a 10G but thats just me, adding more fish to such a small tank would not be the best of ideas. Maybe adding some stemplants/floating plants would help her feel safer.