Can two female bettas ever get along?

Is there any hope in keeping two female bettas alone in a tank together? I had a trio of female bettas that got along great, then one recently ped and all hell has broken loose. One will just not leave the other one alone. The bullied one took to hiding in a cave all the time, until the dominant one discovered that’s her hiding place and now the dominant one is constantly checking the cave (this dominant one seems smart and persistent). So the bullied one has started wedging herself in a group of leaves that rest close to the surface of the water to hide. Sometimes she gets on a leaf that is too high and a bit of her top side is actually out of the water, which seems dangerous to her health to me. I am thinking it would be best to buy a 2nd tank to separate them, but I would be open to buying a larger tank to keep them together if more space would help them get along (they are in a 5-gallon tank now).