Ok, so, I have 7 betta girls in a 55 gallon tank. I wouldn't add any more to that, and that is, again, a 55 gallon. Do not do a sorority in a 10 gallon tank. I misread your post, and then went back and read it just now, and a 10 gallon is way too small. In my experience, you can find websites to back up whatever you want to say, even if it may be wrong. 10 gallons just do not have the room that the females need to feel comfy, and they will fight. You WILL end up with torn fish fins, stressed out females and eventually they will kill the weakest one. I am not exaggerating here. I have personally seen this several times. I asked BFM if a 10 gallon was sufficient and she said no, but my friend went ahead with it anyway, and he had so many problems it was unreal. Bettas will also tend to stay where there is the least water movement, which means, they are not going to spread out that much, at least not enough in the 10 gal, and they will be vying for one choice spot. You have to have a big enough tank that there are multiple choice spots with low flow, and that does not happen in a 10 gallon.
Sure, you can do it if you want to, but next time, if you are not going to listen to experienced members, do not ask for their opinions. I find it antithetical to post asking for help and to ignore the proffered help. Sorry if that was rude, but I think discounting someone like BettaFishMommy, who has YEARS of experience in exactly what you are asking, is also very rude. Just my .02$
Maribeth
If you are upset by this and would like to flame me, please do it in PM. Thank you.