Of course the compliments will help - greatly.

I think there are other things you can do. Like taking her out. Even take her shopping and observe the clothes and styles which draw her attention. Let her know how great she would look in them. Then maybe add in something you like (she likes a pant/shirt combination, suggest a shirt you find attractive too). This would go far in validating a positive sense of appearance. Even let her know how great the outfit might look with some pretty/sexy shoes). Yes it may take an investment but you are investing in her. A sense of feeling acceptable goes hand in hand with feeling sexual. Whatever you do don't bring home some sexy lingerie expecting her to suddenly get excited. I think it sometimes only results in a woman feeling she isn't accetable the way she is.

Do somethings you perhaps don't usually do for her (if you don't do the cooking make an effort to make a meal. If she doesn't go out tell her you are looking after everything so she can have a night with friends)

Show interest in interests of her own.

She needs to feel validated, worthwhile, and accepted. Little things like this will go far into feeling that way about herself. Words of encouragement and compliments will reinforce that.

Yes, it will take an investment of time but it will pay off I'm pretty sure.