Did she jump outta the tank? Or does your 240 have a tile bottom--inside the tank?
I have tile in the tank.
Sad news, perhaps something spooked her and she hit the glass hard, hard bang to the head can end anything....
That's what I was leaning towards. Don't know for sure though.....I know the male didn't harass her because fins were undamaged and no marks were on her from a possible fight