Can My Landlord Do This

So let me ask this question.. I originally went in for my privately owned home I put down the security deposit in the first month's rent six months in my girlfriend moved in and did a new lease and put her name on the lease.. around Christmas I told her I was leaving she put my stuff out and change the locks.. I told the landlord that she had effectively evicted me and I wanted my security deposit back from the original lease since I'm the one that originally rent at the house .. She has gone back and told the landlord I don't know what now the landlord is telling me that the security deposit will have to be split between me and her can he do that?

Can My Landlord Do This