I hated when you fight her when she kept coming back. okay listen up. you should be able to do your big moves by this point what I do is right when she comes back to life I hit her with a big move. Iceman, Gambit, Marrow, Storm..Storm works really good. the first time I fought Marrow for the second time it took me like an hour...when she comes back to life try freezing her with ice man or zapping her with Cyclopes that works too...but hiting the big move with one the xmen I listed before should work ...I hope this helps send me some private messages if you have anymore trouble...I've beat Legends solo at least 3 times so I should be able to help.