You didn't get much advice here on what to look at, so I will throw my opinion in.
Two bows I would consider looking at are the Alpine Micro and the Rintec by hoyt. The Jennings Rack Master light is pretty nice as well. Hoyt and bowtech have some nice womens bows that are more expensive, but you said you were looking for affordable.
Here is my girlfriends bow I got her last year. It is an Alpine micro that I think I paid $190 for.
Here is a link to a thread I started a while ago after she had been shooting for a while. It has a few more pics.
I think she is getting it!
As far as shooting with your wife, I love the fact that my Girlfriend shoots with me. This way when my buddies and I shoot she can be part of it and doesn't feel left out. It is also something we can do together when at home. I want to get her kids into it as well. She has no desire to hunt though, at least not bow hunt. I think I could talk her into gun hunting out of a blind though. I'm almost sure I could talk her into turkey hunting if I could get her to shoot a shotgun.
She shoots well enough that I am getting her a rintec in target colors for her birthday next week. We were at fairly local shop in the next state over and they have 4 models in stock in target colors, three of which she really liked. The rintecs are $380 for target colors and $300 for camo. They shoot much nicer than Alpine micro as far as felt recoil and and the such, but they are 100 bucks more as well. She looked at a rintec when we got the alpine, but for some reason she liked the alpine better. Now that she has been shooting for a while she has changed her mind[
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. Maybe the fact that I can more afford it now makes a difference. I have a better job now and have been working a fair amount overtime.
I like the alpine enough that I might keep it for myself or to teach others to shoot with since it is so adjustable for draw length and is lighter in draw weight.
I agree with the above, do not get her one as a suprise. Take her to a shop and let her try a few and let them set some up for her and let her decide.
Paul