You could get a bigger tank for her Betta...and get another Betta!
Bettas do fine with other fish around them, if you pick the fish carefully. I had a 10-gallon tank for ages, and you can actually keep quite a few fish in them if you're careful about tank maintenance.
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ENTP fits me to a T, though it took me forever to figure it out! DYT Type 3, Enn. Type 1 (hold that thought...enneagram crisis...might be a 7!)
Sparks (9) ;
Spitfire (8);
Sprite (4.5)