Three hours is a risk. It's a "legal" connection but if her incoming flight is delayed, she could easily miss her incoming flight. Depending on your confidence in her abilities, and whether there is a later flight to her destination for the same day, you might want a longer layover. All US (really all major worldwide) international airports would require transfer from the arriving international terminal to a domestic terminal.
What's ideal is a 4 plus hour layover, in my experience, PLUS somebody to meet her and escort her to her next check-in. What I did for my Chinese wife and her daughter years ago, was to just meet them myself at their POE, and drive them home. You could also fly to the POE and escort her the rest of the way.
Faking the need for a wheelchair, is pretty sketchy.