Change in roommate- Nullify/Void a lease?

[Mary Thurman]

I bought a home where my daughter goes to college for her to live in with roommates who pay rent and one of them is leaving next semester but the lease is for the whole school year.  She has found someone to move in the beginning of next semester and so I'm wondering the best way to go about making the switch.  Do I need to do something official to the lease of the girl moving out?  I will have the new roommate sign a new lease and pay a security deposit.  This is my first and only rental property and I'm learning as I go.  Any advice would be appreciated!  Thanks