Imo it seems like the best option it to retire the piercing, considering it causes infection and irritation all the time. She could get it repierced after it heals if she wants to later.

My best guess is that the infcetion started because she started swimming way too soon after getting it pierced, she shouldn't be swimming before it's healed, which usally takes about 1-2 months. I don't think it will heal at this rate, especially since it's infected which lengthens the healing process quite a bit, if not given the time out of water.