My GF's MacBook Pro is running into huge free space issues (getting her into gaming) due to a 125GB Windows partition that is only using ~45GB. Is it possible to resize the partition? Failing that, ...

It sounds like you didn't actually repartition with Boot Camp. Re-run the Boot Camp Assistant and it will almost certainly only show one partition (a 100GB drive will show up as around 95GB because ...

If you are a Mac Boot Camp user and ever wished you could easily re-allocate free partition space between Mac and Windows, Paragon software’s latest offering may be just what you’ve been looking for.