My concern is the high risk of her losing it and as you say, they are not cheap.
@Kittle : Go for it! I thought the same thing when my SIL started one for my 5 yr old. 13 years later and it has never been lost or damaged. It's fun adding milestone charms like sweet 16, school sports, vacations, activities, pets. I just bought a retired graduation cap charm off of eBay that I'll have added in May. It arrives today!