Question Regarding Pet Deposit

[Phil Surdynski]

looking for guidance on Pet Deposit.  Here's the situation on this my first rental:

Currently rented to a couple with one pet dog (small sized).  They submitted an addition fee for the pet per the lease addendum.  The couple has since broken up but one of the tenants would like to remain with a different roommate.   As the pet is hers, do I again charge an additional fee for the dog or not, reasoning that it's the same pet on a new leade?

I want to be fair and do what's appropriate.  Thanks for any help.