She won't go to any women's clothing stores, and her clothes are all too big, but I'll try buying something a bit smaller and seeing how that turns out.

I'll second the idea to buy her some stuff. After my wife gave birth to our first child she lost quite a bit of weight, she was probably 10lbs lighter than pre-pregnancy, not too mention a lot slimmer than when she was pregnant. All of her clothes were ill-fitting, and she simply did not have any desire to go out and buy anything because she was tired from taking care of a young baby.

So on my lunch breaks I would go to her favorite store (Nordstrom), find a sales associate, and tell them I wanted to buy some clothes for my wife. They'd usually ask me her style, I'd tell them a general idea of what she usually wore, and then they'd pick out some stuff for her. I looked at the sizes of her clothes and wrote them down so I knew what sizes to get, and would usually get her normal size and a size down since most of her stuff was too big. I would take the stuff home, let her try stuff on, and then return anything she didn't like or that didn't fit quite right. It was a major PITA, but I was very successful in getting my wife some clothes that she liked and that I thought she looked good in. And I earned brownie points because when we'd go out her friends would compliment her clothes and she'd say "oh thanks, generic name picked them out for me".

The more I did it the more confident I became in getting the right size, and the more she was complimented on her clothes the more she trusted my opinion on stuff I picked out for her. And it wasn't especially difficult, like I said I just asked a sales person to help me out and they'd tell me stuff that was popular and I'd pick things that I thought looked good.

So if you're going shopping for her I'd find out her size and find out her favorite stores. The first time you do it I would also recommend you buy things that are a little nicer and more expensive than what she'd buy herself, and only buy a couple of things, like maybe two tops and a pair of pants. Also bonus points if you can figure out what colors would look best with her skin tone (here's a start ) . And make an honest effort to buy something she would like, not something you would like. If she's into baggy black clothes you're better off getting her a top like this in black over a top like this in pink