J.O.
My best advice is to buy one of 3 or 4 kinds, and let her guide you, all 7 of my kids used a different kind, I'll list a few pro's and con's with each...
Playtex w/bags.....no real complaints much easier to keep clean.
Playtex Air.....good but does start to leak out the bottoms very frustrating.
AVENT........leeks around the nipple after a couple of months.
Basic Gerber style....good and you can find them anywhere, good thing if you walk out the door and forget a bottle!
Dr. Browns.....a little pricey but nice.
Glass or plastic I have always used plastic glass is to heavy and I hate the thought of one shattering!