I hear you, over the years the various places we lived always seemed to have a person like that, grrrrrrr!!
Mom had a neighbor like that who would pick the roses or pears, her answer was that no body was picking them (meaning us) so she hated to see them go to waste.
The nerve!!! We were always brought up and taught not to tresspass on other's property, oh where has respect for others all gone?
Sorry to hear all your hard work fell in the hands of this rose thief, I hope she gets pricked good by the thorns.
Take care now,
DE