YES, it will DEFINITELY effect her ability to nurse. I had problems with my son until we figured out he was tongue-tied (it was not noticed at birth). He was able to latch on so much better minutes after his tongue was clipped. We had it clipped when he was about 10 days old.
You can go to an ENT and they use a local anesthetic put on with a cotton swab. They have a special tool that clips the extra skin, there is a few drops of blood, and it is done. My husband and I were a wreck, but my son actually SLEPT through it! We were literally in the office for FIVE minutes. My son gave out one cry when the clip happened, then went back to sleep -- literally. After the clip is done, the baby has full use of the tongue immediately -- it is actually quite amazing.
If you don't have it done young, you can have it done later but it is far more complicated, more pain, more chance for complication, the child may have to relearn how to speak certain things, etc. It can likely effect speech development, which is why we decided to have it done before speech even developed. We use drugs/surgery only as a last option when other more holistic methods have already been tried.
I know it sounds scary, but I would do it again if in the same position again. If you have any questions about our experience, I'm happy to share. Feel lucky that your doctor noticed at birth so you have the choice to decide what you'd like to do.