residental easement, legal advice needed

I own a parcel of land which has an easement attached to it which
gives two of my adjacent neighbors a right of way to use 50 feets more
or less of my land for road access, ditching, and utility use. In the
road maintenance, it says that all three owners should share one
driveway. In the past, only one owner use the right away.  Now, the
other one just decided that she wants to put up a road in her
undeveloped land which she plans to live there when she retired. Thus
she will start using the right away in my land as well.  During the
construction process, I learn that she wants to clear out some trees
along the 50 feet lines in order to make room for her road which is
not a problem in a certain area.  However, I have a hilly driveway
which I feel is supported by the trees below, along the 50feet lines. 
Can I ask her not to use the entire 50feet, say 30feet?  She insists
that she needs to clear the 50 feet area to make room for the road.

The other question I have is regarding the other neighbor who also has
the right away in my land.  His land is not landlocked, and until this
day, I do not understand why he needs to use my land for road access. 
The northern border of his land is bound to a town road and he can
access the road through that area in his lot without having to use my
land at all.  The easement was already attached before I bought the
land.  Is there a way I can relinquish this easement?

Thank you so much for your advice.

landowner in distress.