What is RLV?
RLV is a feature found in certain Third Party SL viewers that can enhance your SL experience.
When enabled on the sub's SL viewer, it can allow scripts to do certain things, like prevent the sub from detaching certain attachments, or force the sub to take off (or wear) attachments, or clothes, etc.
Which viewer
LULU supports RLVa (a flavour of RLV), and recommends the Firestorm viewer. The official SL Viewer does not come with RLV.
Some other viewers (e.g. RestrainedLove Viewer, Cool Viewer) support RLV, not RLVa, and certain features of your LULU will not work in those.
How to turn on RLV
In Firestorm, there is a an RLV tab at the top-level menu. Where to enable or disable RLV differs between different SL viewers.
Abuse
If the sub feels that the RLV features are being abused, and wants to out, she may do so any time by disabling the RLV on her viewer, and relogging. Upon relogging, she will be free from whatever RLV restrictions that were placed upon her before, and she can detach (or get away from) the objects that were putting the restrictions on her.