I am guessing with that weight and your measurement, you are both very petite. I'm 5'6" and my narrowest waist measurement is 29" and I'm pretty slim at 120 lbs.
Fatty cuts of meat are one obvious way to keep fat counts up. This is preferable if the meat is good quality, but if conventional meats don't bother her, then you could still use those (if price is an issue). And fish!
If you visit Whole Foods or another health food store, you can probably find a nice selection of various cooking oils to work with so it's not all butter and olive oil. I don't really know what else is out there, but I know people like red palm oil (I think that's what it's called?). You may want to test that with her in case of allergy, however.