I'm so sorry about your brother-in-law.
A few thoughts:
1. Get a bird that was hand-raised. They are much better adjusted to people.
2. As far as cages, the bigger the better. The most important feature of a cage is how easy is it to service (change the litter, clean, open & remove bird, refill food & water dishes).
3. Consider getting a bird who needs to be rehomed. Check with animal shelters and newspapers. My parrot had been in three homes before mine and he is the sweetest fellow you'd ever seen. Much cheaper to get a re-homed bird too.
4. Look at the bird section of Drs Foster and Smith: http://www.drsfostersmith.com/Product/Shop.cfm?N=2003
Check out the pet education section for articles about bird profiles, care, behavior, etc.
Birds are wonderful companions. I think she'll enjoy one.