Okay, looks like I should have given much more background information... she's been training with me for about 5 months. She had major back pain when she started with me, couldn't get a diagnosis, and she's gone to a chiropractor regularly throughout the time we've been training (as well as before). She's had a bunch of kids, and has excessively lordotic posture, which is what I think is responsible for her back pain. Her legs were extremely weak when we started training, and she struggled to do squats without any weight. She also struggled with even activating her abs, which were also very weak. Her hamstrings were also extremely tight, and it took her a while to work up to full range RDLs. She also had very tight hip flexors and poor glute activation.
After the first month of training, she no longer had chronic back pain (but she continues seeing her chiropractor for regular adjustments, she switched chiropractors around the same time she started training with me), and she worked up to doing squats with the 45 lb. bar, RDLs with 45 with full range, and all her other exercises without feeling back pain. During that time, she never used the bar pad and never complained about it.
Over the last 4 months, she's worked up to doing squats with 95 for sets of 8, deadlifts with 120, barbell glute bridges with 90 (yes, she uses the pad on those at least), and has not mentioned anything about back pain or pain from doing squats.
This week, 2 days after doing squats, she had a lot of tension in her traps when she went for her regular chiropractor visit. He told her to use the bar pad when squatting heavy. Mind you this tension never was there before, and she had been gradually working her way up in weight for months. Her posture is now much better, she's way stronger, way more flexible, but suddenly her chiropractor thinks it's my fault for her having a bunch of tension in her traps one time.