lt would be useful to know a little more about what she likes. Do you ever compliment her on her perfume? That might be a way of starting up a conversation to find out what she might be looking for in a scent.
A nice thing to do would be to take her out for a sniffing trip around your local department store/mall to see what she likes. Combine it with a nice lunch somewhere & you've given her a lovely day out!
Welcome to basenotes!