On the front of her leg just below her knee on the outside of her leg? I was having a similar problem recently. It was mostly affecting me climbing. It appeared to have been a combination of an old ankle injury, a muscle imbalance in my upper leg and misaligned knee caps (which I gather is something many women have - knees that aren't in alignment with our ankles).

Apparently the head of my fibula wasn't moving at all which was causing the "knee" pain. My PT got it (and my ankle) freed up and gave me some exercises to do to to help strengthen the weak muscles. It vastly improved after just seeing her once, though I have been back in for a bike fit/cleat fit tweak and two more sessions. I've got one more appointment, but she thinks I'm pretty much done and OK - and my knee isn't bothering me at all anymore.