There are several factors that will contribute to her breastfeeding success after a reduction, such as what type of reduction she had (whether or not the nipples were removed). If there is a lactation consultant available to her in the hospital, I highly recommend she meet with them, if possible more than once. She should also try and latch the baby as often as possible early on to promote good milk production, even if she is afraid she won't be able to nurse in the long run. Chances are she will still have at least some milk ducts that connect to the nipple.
I am currently breastfeeding after a reduction and seem to have just about enough supply for my baby. I think our major challenges are actually the baby's latch rather than my ability to produce. Due to the surgery one of my nipples is more difficult than the other for my baby, so that side is more problematic for her. To help with that I alternate which breast I start with (if she's frantic with hunger I start on her favorite side, but if she's feeling patient we start with the trickier side). Different positions also help. I intuitively kept trying the cradle hold but the cross cradle worked much much better for us, as does the football (clutch) hold. Your friend may notice her nipples do not point exactly the same way or do not have exactly the same composition, so different positions might work on each side, or the baby may favor one side over the other. For example I can only nurse laying down on one side with great difficulty, but the other side works fairly well.
She may find that pumping helps with getting her supply up or to get her nipples to cooperate more if they are flat or difficult to latch onto.
With my first daughter we had a lot of difficulty (some of it due to unrelated factors) and this time around with my second things are going a lot better. Even if your friend isn't able to nurse this baby, she may still have success nursing future babies.
Also help her remember not to give up right away. Sometimes just one day of nursing can feel like an eternity and if things aren't going well, it can seem impossible that it will improve, but often just a couple of days later nursing will be completely different already.
Good luck to her, I hope everything goes well for her with nursing!
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