Fore/aft position

[OakLeaf]

Offset might well be your issue, but check seat height first. If your saddle is too low, then your knees will be over-flexed at any given position. The general rule is that at the bottom of the pedal stroke, you should just be able to put your shod heel on the center of your pedal with your knee extended but not locked. If you've already done this and I missed it in another thread ... then offset is probably it, and sorry for the repeat

ETA - just reread your OP and saw where you're not having problems. My first rule is if it ain't broke, don't fix it. It can be enlightening to play around and experiment with fit just for greater comfort and power, but if you're on a tight budget, I don't think I'd necessarily shell out for a new seatpost just to see. If you have a local swapmeet or find something on TE for not too much money it could be worth a try, but other than that...

The other thing is cleat position. Are they directly under the ball of your foot?

[indysteel]

Good thought about seat height, Oak. I might be misguided in saying this, but fit on a mtb has additional dynamics to it because you don't just sit on the saddle miles on end like you do with a road bike. While I did some time and money tweaking the fit of my mtb, I didn't obsess about every millimeter like I have on my road bike. So, from the OP's perspective, I might just keep riding with the current set up and play any component changes by ear.

I looked up the OP's bike, and if I have the correct model, she already has 20 mm of offset with a 74 degree seat tube angle and a 31.6 diameter post.