No, unfortunately, there is nothing you can do to get off the lease. A lease is a contract; a contract cannot be altered by one party--including to remove that party--without the consent of agreement of all other parties. That means to get off the lease, you'd have to get your neice and the landlord to both voluntarily agree  to let you off. And the landlord will almost certainly not agree to this, since it reduces the number of people the landlord can hold accountable for the rent without giving the landlord any benefit.