How much worse can she be than any other action star then?
Shrug, not really my point. She has no acting chops whatsoever, and they're just throwing her into a leading action role with all of these other established talents around her and asking the audience to accept that she's awesome on screen just because she kicks ass in real life. It's a movie, aka fantasy/fiction - it just doesn't work that way, and frankly she's not hot enough to pull in the drooling tween audience either (esp with zero name recognition). The only people I see going to see this movie are MMA junkies (even then, I'm not sure how popular women's MMA is compared to men's) and a random smattering of people who will just go see anything.
I'm probably coming across stronger on this than I actually care about it in real life, I just don't understand the decision from a business standpoint. The whole thing looks like Bourne Identity but without Bourne.