Descendants of Avalon by J Lynn Else
Genie's parents are getting divorced, and it's all her fault. Her best friends, Beth, Mei, and Whit, convince her to make a wish in the small Minnesota town's antique well. Genie thinks it's ridiculous, wishing for her parents to reunite, but what can it hurt? She's already ruined everything.At the well, a mysterious woman with a walking stick and twigs in her hair, like some sort of homeless mystic, warns the friends to beware. Their wishes are powerful magic. Scoffing at the notion, Genie and friends toss their coins in. That night otherworldly creatures try to kidnap each girl. Only Beth is captured.The three remaining friends gather at the well. A mysterious guy named Tristan says he knows where Beth has been taken. Only the power of Genie, Mei, and Whit's combined wishes can save her. Genie can't believe magic tied them together, but after her scary encounter the night before, she can't deny magic might be real.The friends agree to follow Tristan through a magic portal and step into the legendary island of Avalon, a land separated from Earth after King Arthur's death. With the help of some young descendants of the original knights of Camelot, the Lady of the Lake, and Morgan le Fay, the three teens set out on a quest to rescue their friend, battle an evil sorcerer, and save two worlds in the process.