If it's an infection due to an abrasion then it seems like it's gone but it's not really gone until the doctor gives her an antibiotic. Usually gone within a matter of days after that though. He can give her an exam and some advice on how to prevent getting another abrasion.
Since you're doing Penis Enlargement, it can cause cuts and small tears inside due to change in size sometimes. (It's happened to me a few times already). She should always keep a check on herself with her OB-GYN anyway because change in cells in the cervix(ie: change in penis size stretching her cervix more) can cause cancer cells(cervical cancer). It's not a very high risk at all, but can happen if you make fast gains, and always a good idea to keep a check on it just in case.
Also, if you ejaculate inside of your girl and she doesn't go pee right afterwards(pushing a lot of it out), then it can cause yeast infections. Which is what the infections you're talking about sounds like to me. She can treat those with OTC meds such as montistat and be done in a week, BUT...you can get it and not show any signs, but still give it back to her every time you guys have sex. If it sits inside of your prostate, it can be really nasty after a while LoL. So she should always go pee afterwards and push some of the sperm out of her to keep from that happening.
My advice would be to go to an OB-GYN and get checked anyway. He can also give her medication for you to clear up any yeast infections you get from her, advise her on how to prevent the burning and give antibiotics for the abrasions and stuff. Plus, it's a good idea to keep the health of her female organs up to date, heh.