Harness Sizing Help

Hello! I was hoping you guys could help me with a sizing question for Black Diamond momentum harnesses. I (F) climb a lot and my girlfriend isn't a serious climber but likes to come occasionally and always complains about the rental harnesses, so I wanted to get her one for Christmas. It would be a total surprise so I don't want to ask her measurements but I'm not sure how to size it!

She's 5 feet tall, curvy, and about a US size 12-14. I was thinking a large but I was wondering if any shorter/curvier climbers would have some input on what would be the most comfortable.