I've done soriority's 3x now, the first with 5 in a 10 with silk plants, the 2nd in a 29 with 10 or so girls in a half real half fake plants (all added at once, horrible lifeless brown colored from walmart when they had em on discount to get rid of them when they decided to drop selling them, perked up right away and got pretty), and like 20 or so in a 55 gallon moderately planted. Also all added at once. I've never had any issues cept when I tried to add a girl who was a third the size the other girls when I added em all in, she got picked on. It's best to add em all at once, just watch the params. In your case, if you want to go the sorority route, get your other girls (all at once, just test daily to keep your water quality up) then remove your current girl. Re arrange the decor, you want lots of places for them to hide too and claim territory. Add all your other girls, then add your current female. Watch for bullying, but Ive never had it happen cept for the pint sized baby female I tried to add.