I had a ruptured appendix when I was fifteen that wasn't detected properly, became infected and very nearly killed me. Luckily things have improved a lot since then and hopefully she should be fine and back on her feet within a few days.
G_d Bless
A few years back, my fifteen-year-old niece did not feel well at my daughter’s wedding, her mom ended up taking her to Urgent Care, and they missed the same thing, this was in 2006. My sister took her to the E.R., she was admitted, it had ruptured, and I am thankful to say, she made it. She was on anti-biotic therapy for a long time after that, her recovery was slow.