Is mom in hot water?

My mother and her friend both signed a lease on a house in Texas about 6 months ago. The roommate has since moved out leaving my mother with all the bills. Is she now responsible for the full amount of the rent or only her original half?

What does the lease say?

Is it a contract between the landlord on one part and Mom and the boyfriend on the other part?

Does it say anywhere in the lease that the two tenants are jointly and severally responsible?

Also, check Texas law if it says anything specific about this.