How to recover faulty USB drive

This is going to look like a list pf product recommendations, I'm afraid…
…but Mac can't natively write to NTFS, so anything that could 'fix' the drive is going to need to first be addressed through an NTFS enabler. [This is technically possible for free using FUSE, but it is often flaky & I wouldn't trust it for any critical task.] Paragon NTFS for Mac is the one I use. Combined with Paragon Hard Disk Manager you may have a hope of actually fixing the structure.

Once you can better access the drive, then scavenger software such as Disk Drill might be handy, if the structure itself cannot be repaired..

If you're happy playing in Terminal, then dd is built-in & free. See http://hints.macworld.com/article.php?story=20050302225659382 for some usage guidelines.

A common suggestion for data rescue is TestDisk, which frankly I've never been able to make head nor tail of. It just complains you must run it as root… not sure how you're going to do that on a mac.

All of these methods except the first - trying to fix the drive itself from Hard Disk Manager - will require you to have sufficient spare drive space to recover to. You want to avoid at all costs actually writing to the drive you're trying to recover.

Alternatively, test if the enclosure has failed - remove the drive & connect by an alternative method. This would be easier if you have a big ol' Mac Pro with lots of spare drive slots; otherwise you'll need a hardware dock of some sort.

You might consider a fourth option - a data recovery specialist.

..and then recommend to your friend they ought to consider backups to be an important part of running a computer.