You're the one who wants to end the lease early, or be replaced as a tenant. By all appearances your ex-roommate has acted diligently in response to your announcement that you were moving out. You can try to find a replacement roommate that is acceptable to your roommate and landlord, or you can help her with a renewed search; otherwise, unless your ex-roommate decides that she also wants to terminate the lease, you'll remain a tenant under the lease through June of next year.