Has she been paying rent? Does she receive her mail at that address? The LL knows about her. She's a tenant even though she's not on the lease.
If you change locks you will end up in court. How long have you allowed her not to pay her share of the bills?
My suggestion is that you and the other tenants get together and sue her in Small Claims court for payment of bills. If she loses you can apply to have the judgement recorded on her credit and it will (maybe) mess her up for a while as being a deadbeat.
The lease does not provide for subleasing. The tenant is purposely excluded from the lease because "because even though it's a 6 bedroom house, law states that only five people can legally live here." A court action will not be successful. One must come to the court with "clean hands."