There are quite a number of health benefits and you've already stated one that you've experienced (relaxation). I'm sure you've noticed others, but you may not have pinpointed them to being from reflexology (digestion, stress levels, and many others). I'm sure you could ask your girlfriend for a list and you could point out a dozen of them that you've noticed since she started doing the reflexology.
As long as she's well trained and knows what to do, there's not much of any risk per se... but if she pushed on the wrong pressure points, it could hurt. No offense to her, but I'm willing to bet she might have accidentally done that a few times early on, but I'm sure she's gotten better over the past year... it's common to make minor slips like that early on ;-)
Good luck with the relationship and I hope I helped!