NG,

Let's say you decide not to implant a root barrier between the two
properties. Another method of control would be to dig a trench between the
bamboo and the neighbor's property. Wandering rhizomes will be visible as
they try to cross the space and can be removed. Someone might know how deep
and how wide the trench should be. Also, bamboo (except for maybe a couple
of types with rhizomes with air spaces) won't be able to cross standing
water such as a water-filled ditch or trench, or pond... that is, if you
have water to spare. There're other methods of control on the ABS site.

As for the neighbor, keep the bamboo she lopped off, spray paint it green,
and when Spring comes, under cover of night, stick it in the ground all
around her yard.

D.G.