Of course Marriott associates the form with a particular associate and that associate has visibility into the form's use, although practically it won't usually arise.
Where this comes up is if anything goes wrong down in Florida, even damage which you accidentally cause or if someone travelling with you has an incident of any kind down in Florida, Marriott comes back to its Associate to make it right. In effect, your friend is vouching for everybody staying on the rate.
Only you can answer the question of whether it is worse not to inform your friend in advance or worse to have your friend find out because one of your family members accidentally trips into the TV and trashes it or some hyper-sensitive neighbor complains about noise from your room.
Lastly, while it is extremely unlikely, as you are likely aware, Marriott does spot checks on the use of these forms as an anti-fraud measure. What will your friend say if she gets a call asking her to verify that you are OK to use the form in FL?