What an amazing mother in law you are! I hope I a MIL like you someday, hehe.
Well first I would start by getting her fitted for a bra. Until you do that, it's pointless to even try to shop for tops. Don't trust her when she tells you her bra size! I don't trust most women with their bra sizes. I myself once wore a cup size too small and a band size too big, and that is the same mistake most women make.
Look for knit tops with open necklines and avoid at all cost anything with a high neckline. It's hard for me to give much more advice without seeing her, but being busty and petite myself (though not THAT busty), I can relate. Since spring is coming up, how would she feel about picking up a few dresses? Jackets look particularly good on busty women. A fabulous denim jacket and another fitted jacket in a different material should be a good start.
For bottoms, I don't think any body type can really go wrong with some bootcut or trouser jeans. Just grab a whole pile in her size and have her try them on one after the other. It's the only way to find the right brand and cut.
And don't forget accessories!
OK, that might be a lot for you. I'm not sure what your budgeting for her, but those are some ideas.
What is her style, personality, and taste like? Does she work? Is she a SAHM? If she works, what kind of place does she work in? Answering some of these questions might help us better advise you.
