didnt do the 21 combo, have finished that mission and saved since then, is there another point to get her?

hope i didnt miss my only chance.....

You missed her and in turn miss another character down the road.  If you do the second play through don't forget to do the 21 hit combo.

I think with most characters in the game, its a one shot deal to get them. That's why I make sure to have multiple saves and or to understand for next time around to get them. Most have special criteria that is needed to acquire them.