Cervical cell changes related to HPV can development in weeks or months, but in some cases do take years. Most of the literature refers to an average period spanning weeks or months, however. Cervical cancer, on the other hand, which is a rare outcome of HPV infection, does characteristically develop over many years, often 5-10 or more.
It's true that abnormal cell changes often self resolve, especially in younger patients. However, the need for treatment is predicated on a number of factors, such as just how extensive the abnormal cell changes are, their size and exact location, and so on. Ask her health care provider to explain why he/she is choosing one course of action over another, and if there are reasonable alternatives to surgery. LEEP is not uncommon, though, especially with moderately abnormal cell changes.
I hope this helps, but post again anytime.