Personally, I would reccomend a taser.
Have you ever been in the vicinity if someone spraying pepper spray? Believe me, it's nothing like the direct, non-room-filling water squirt you see in the movies. If she uses it, your daughter WILL get a face full of it too. Not saying it won't be effective, though. Regardless, I would check out OfficerStore.com, they have a ton of mace, pepper spray, tasers, etc.
My wife used to carry a screamer before I met her. Then she went to a cheap taser, which she felt more comfortable with... But she prefers her Sig Sauer now