The grass strip between the paved sidewalk
and the granite curbstone where Laura has placed
two small boulders is not your property. That
grass strip belongs to the Town of Belmont.
It is part of a public way, obstruction
of which by an abutter is illegal and might 
arguably contribute to a serious traffic accident.

At such time and under such circumstances as
would not contribute to intrafamily conflict, 
I would ask her to remove the boulders.