Well, I have an update on player x. She saw my preferred soccer/knee orthopedist in town on Wednesday. He examined her and read the comments I gave to her mother as well. In summary, he agreed with me that she had patello-femoral pain/inflammation.
He also told the mother she had just gone back to soccer too quickly and never fully regained her quad strength. He told her if she continued to work around the deficit, she would likely suffer another injury. This is often the case. So, at this point the plan of action is to take a one month hiatus from soccer and do formal rehab three times per week.
While this process will be much slower and less active for player x, it probably will be for the best in the long run. In the short term, she may suffer some loss of fitness, but she needs to focus on strengthening right now. I will keep you updated on her progress as time goes by. She will likely return to me for conditioning to transition her safely back to full soccer once therapy winds down.