Cin 3 is not cancer. It is pre-cancerous cells. However they do not always turn into cancer. Unless it is abnormally aggressive, it takes many years for cancer to develop.
A .L.E.E.P is a very common procedure and cervical cancer is among the most treatable cancers. Cervical cancer is directly related to the .H.P.V virus (not the kind that causes warts, the high risk kind. Although you can have both kinds.) that is sexually transmitted. No one is sure the amount of people who have .H.P.V, the estimates are in the 80-85% range of sexually active individuals. Interestingly, celebate people (nuns) do not get cervical cancer.
Cervical cancer is not inherited, so you wouldn't have a higher risk of having it because your mom did.
In about 4-6 months she'll have another pap smear to make sure they got all the bad cells. L.E.E.P is so effective (i cannot remember the percentage...But near 90, I think) that usually only one 'treatment' is needed.
I hope your mom is doing ok! I know it can be scary. Good luck to her.
Ps. She can exercise a few days after the procedure. It is an easy recovery and quite simple.