Female Betta fish staying out of the water.

The female started jumping to get itself sucked to the glass outside the water. Strange behaviour. At first, I thought it was because of the male. But the male betta is so peaceful and never attacks the female. I even tried removing the male. But the female Betta continued this behaviour. I did not worry much because betta fishes are able to breathe outside the water as well.
After a few days, the female got sick and died.