How it works here -
If your friend doesn't accept the repair, her agent should call escrow and tell them not to release to record until further notice. Then she tells the seller why, and what she wants done about it (recommend against asking them to fix it again, instead, ask for $$ for the work to get done) See if the seller will work it outside of escrow, so the financial aspect doesn't change on paper and the lender doesn't want to review the transaction again.
Seller has the option to ignore your friend, and wait for the contract to expire and sell to someone else. In which case, your friend would likely have to file suit for specific performance if she really wanted it that much.
If the PVC is accessible, your friend should ask herself if it's worth it to cause a problem or just suck it up and replace it. For my friends, I'd offer to fix it myself to save them the headache.
I'm not giving you legal advise.
ETA - As an agent, I would be extremely annoyed if a buyer waited until the day before closing to reinspect. Really should happen quite a bit before closing if at all possible.