well, the video taping is quite likely legal but the peeking in windows surely isn't. A call to the police to report that would be appropriate if you care to.
as to how soon you must do something, that is something more for the courts to decide and it isn't clear what they might decide. Here is an excerpt from a Wisconsin case concerning the abandonment of an easement:
d. Nonuse. Conduct from which an intention to abandon an easement may be inferred may consist in a failure to make the use authorized. Nonuse does not of itself produce an abandonment no matter how long continued. It but evidences the necessary intention. Its effectiveness as evidence is dependent upon the circumstances. Under some circumstances a relatively short period of nonuse may be sufficient to give rise to the necessary inference; under other circumstances a relatively long period may be insufficient. The duration of the period of nonuse, though never conclusive as to the intention to abandon, is ordinarily admissible for the purpose of showing intention in that regard. .
In other words, they are saying "it depends"
so, what I would do if you do not want to actually fight this at the time would be to use the easement up to the fence. Even if that means only driving down the lane, turning around, and driving back. Kind of hard to argue abandonment when there are tire ruts in the ground.
since you do not want to confront the person at them moment, not much else you can do. If it were me, I would move the fence (without actually damaging anything) and use the easement. She would either call the police or sue you. If the police come, they have the option of not getting involved or do something. If they are smart, they will stay out of it. If they agree with the other person, they might cite or even arrest the offender. The charge should be easily defeated by proving the right to use that land. In fact, it is she that is acting illegally (although hard to put a criminal charge on it).
If she sues you, then you will have your day in court.