Unless your daughter is a big "baby doll" girl, I woudn't get a Bitty at 5. I know alot of girls in DD's class wouldn't have anything to do with a "baby" by kindergarten or so.
The AG dolls are very well made, unless your daughter's very destructive, she's not going to hurt it. The biggest thing is their hair. You need to use a wig brush on them (I got DD's at Sally's Beauty Supply for about $3, you don't need to get the AG one for more.) That brush (and any hair do dads) need to be used JUST for the doll, not on people or pet hair.
As for getting it cheaper, short answer is they do not go on sale. Occasionally there is a code for free shipping and sometimes $10 off coupons can be found in the movies when they come out.
If you're willing to get a used one, there are sometimes deals out there if you look. I've not spent more than $20 for the ones I've bought (from Craigslist, Goodwill and a lucky raffle ticket bought at the church fair.) I'm always on the lookout, though! Ebay also has some also, varying amounts of "bargain.)
Check out
www.agplaythings.com- great site for all things AG.
eta- books, the historical's books (each has 6 of them, Rebecca's only got a couple so far, though) are easy read alouds. Be forwarned though that their are some tough subjects in them. Kirsten has a young friend die in the first one, Addy is beaten by her master... These are unavoidable sort of realities in history, but may be too much for your daughter. Check them out from the library and read them yourself before you get stuck in a tricky chapter!
I've found the girl-of-the-year books (the current girl of the year is Chrissa and friends, there have been various others past years) are at much higher level. They're longer for read alouds and "heavier" topics. I started reading Mia to DD8 last year. It was really over her head and we never finished. The historical books better for the younger crowd.