you know, if she already knows, and you don't know how/what to buy, you might as well just take her to the store and be like "ok honey you got xxxx amount, pick one"
That way:
1. she can't not like it because you are a total idiot when it comes to this crap
2. It also saves you an abundance of time not thinking about what to get
3. you could even use that time to check out bikes