powder puff tree

hi guys

my sister lives in Florida, and has just cut down a powder puff shrub/tree. I think its called a calliandra. she has got down to the roots, and wants to know how to get rid of them completely as she is worried they are very near to her house.

ive had a look online, and all I can find is don't plant them as they are invasive or how to care for them!

she was thinking of putting bin liner on the roots to stop the sunlight, I haven't heard of this, then drilling holes, but ive only heard of doing this to a tree stump.

baring in mind this is florida, where things are tropical and plants can get out of hand, any ideas on how to get rid of the root?!!

many thanks