Low brake pedal?

Working on my daughter's SUV listed above. She had someone put new front rotors and pads previous but stated the pedal had always gone way down ever since she bought it. I adjusted the rear brakes which were in good shape and proceeded to bleed them out rr, lr, rf, lf. Although the pedal improved, it still went way down. After bleeding several times and no improvement, I ordered and installed a new master cylinder. After bench bleeding and installing, I again bled all the brakes and there was no improvement. I had read a couple of threads about running it on gravel and sliding the front wheels to get the abs to engage, I did this multiple times with the abs engaging each time and the pedal still goes way down. I have a friend that has a scan tool to do an ABS bleed but should what I did on my driveway helped at all?