Jokes and SJW claims put aside... She's not wrong though. It would be neat to have more female characters. And hopefully... Not (always) behind a paywall (we, gamers, are never happy are we?)
I won't complain about the current roster. I mean...No one seems plain and that's a good thing IMO. It makes them stand out.
Ana is the token "alt-style" character, but would you really say that a goth/punk hybrid doesn't fit the killing floor-verse?
Rae is a bit trickier with her rockabilly outfit, but again...She makes for a very peculiar character that stands above the crowd. Her tattoos are stylish and her accent is cute (even if her voice might bother some people).
Mrs.Foster on the other hand... Eh, can't say I enjoy genderbent characters that much, but I guess that doesn't happen that often either? Plus its fan-service.
BUUUUT yes, we could definitely use some others. I agree with that. Why not a middle-aged woman for example? You're speaking about ethnicity, but we very rarely get to play female characters above their 30s... That'd be also quite fun.