I think it's fine. If she was a friend who you saw socially, then NO, but someone you work with? Sure. So long as the "kinda chemistry" means you do actually chat to this girl and it won't be totally out of the blue.
I went out with a a guy at the last place I worked. I was halfway though writing an email, but decided it was way too cowardly. So I asked face to face, in the office. I just said "are you busy on Friday night? Would you like to go out for a drink?". He said yes. Then HE emailed me, saying I was brave to ask in the office, heh. I look back and cringe -- I shouldn't have done that in front of coworkers.
Certainly if someone came to my desk and asked me out in the office I'm in now, it'd raise a lot of eyebrows and I think it'd take a hell of a lot of guts. If it's really going to be awkward, I think an email is ok. I'd have no problem with it at all if someone at work asked me out by email. I'd only consider it a cop out if they had plenty of opportunity to do it face to face.
I'd want a short and simple email, like what the person would say to my face. Save the content and conversation for the actual date. I wouldn't want an apology or comment on the lameness of email -- if it's the right thing for the working environment you're in, it's not necessary. You can always talk about it later.
It also depends on if she's after someone with BIG BALLS, or normal balls, or if she has so few balls herself that she's relieved to not be put on the spot.