My 92 year old mom has trouble opening and closing fairly new windows

Are they wood, metal, or vinyl? Regardless, you need to CLEAN the sliding surfaces as best you can (get out all the dirt, dead bugs, etc.),tooth brush and Q-tips are good tools to use. If wood, try waxing the sliding surfaces using paraffin, like the block used to seal jelly jars or a candle. If aluminum, use a fine steel wool to remove the oxidation (it's white and powdery) then clean out (vacuum) all that oxidation "dust", and then use WD-40. If vinyl, do NOT use WD-40 as it will soften the polymers and make the windows stick forever; use a silicone lubricant after you've cleaned the surfaces mentioned. (It is safe to use silicone on wooden surfaces, however.) NOTE: it is possible that the windows are out of plumb due to incorrect installation or age; or that weather stripping has shifted, or that someone at sometime PAINTED the sliding surface. That will require removing each sash... Good luck, try cleaning-and lubricating appropriately-first.

Try rubbing the tracks with wax. This will hold up and last longer then WD-40.

Believe it or not, but the original Pam works better than WD40, even on wooden drawers that stick.

If your windows are vinyl, try furniture polish in the side tracks, this works for me, try it. Good Luck!

Rub cake soap on the bottom. Open, close window several times. Repeat. Warn mom not to try to open window with usual gusto or you will be looking for it in the neighbor's yard ;)

thank you!