I am 27 now and have 15 missing teeth. I was also an active little kid and knocked out a few of those baby teeth, so keeping those wasn't an option.
I spent my teens in and out of the offices of four dentists: my pediatric dentist who kept me in temporary bridges from age 4 on, my orthodontist, my cosmetic dentist, and my oral surgeon. I got braces off and waited two excruciating days without two of my front teeth while waiting on the flipper, which arrived a day before cheerleading tryouts in front of the entire high school. I lived it, and it's not that bad!
My advice would be to fight your medical insurance companies on this from the get go. My mother fought and fought, and most of my dental implants were covered; because it was oligodontia, they argued it as a medical condition.
Try to plan treatment plans around her extracurriculars, so that she's not missing out on anything because of this condition. I know it can be costly, but if you keep her in partials/flippers (i.e. a retainer with teeth attached), no one will ever know. She will probably be a little self-conscious, but there are SO many ways to conceal it, and you KNOW she's not ever going to lose that retainer!
My doctors started placing my dental implants during my junior year in high school, after my jaw was done growing. Pain-wise, placing a dental implant is much less painful than an extraction. She'll probably have to have several bone grafts, since the bone will be thinner and weaker in areas where missing teeth should be. My mother opted for an oral surgeon to place the implants as opposed to a periodontist; in terms of training, each can do a fabulous job with dental implants, but an oral surgeon will have the added benefit of general anesthesia that is more readily available for procedures. If you are not opposed and the cost isn't prohibitive, general anesthesia makes the procedures less scary. I was awake and lucid for my first procedure, a gum and bone graft, with my new periodontist just last week, and I would have been scared to death at 16 or if I wasn't an old pro at this.
I grew up as a normal kid though, with my false teeth and all. I was very involved in middle school, high school, college, and law school. If your daughter was already taking on leadership roles 3 years ago, she will probably be confident enough to handle this.
Just be financially prepared, find excellent dentists that know what they are doing, and try to minimize disruption of her school life.