Lease Termination

[ch14h]

We recently moved into a new apartment, though our lease doesn't expire until May 2003. I found several suitable tenants to either sublet or take over the lease. My landlord told us that if we did not find someone suitable by December 24, she would rent it at 60% of what we are paying to her friend, and would keep our entire security deposit. (Which is 2 months rent, and a substantial amount of money.) On December 21, I found two potential tenants who wanted to lease for the exact term of the lease and were willing to put down 3 months rent up front (which covers most of the lease). The landlord agreed to meet with them, but because of their "limited" credit, she says she is not comfortable renting to them. However, she rented the apartment to me, and my credit is in the lowest 1% of the population. The only real reason she gave us for denying these potential tenants is "a gut feeling."
I don't think that it is reasonable for her to rent the apartment to her friend at such a reduced price and keep nearly $4,000 of our deposit. She has not made any attempts to look for another tenanant, and is set on renting to her friend. I would like to sue her, but have no idea how to go about this. I plan to speak with a lawyer, but I'd like to know if anyone had thoughts on our situation. Thanks.