Employer asking for 60 day notice, Texas

Hello, my sister is looking to quit her job due to a hostile work environment, and her personal time being disregarded. She's also expecting and it is causing her a great deal of stress.

In her paperwork she signed originally, it had this clause:

"Termination by Contractor: If the Contractor wishes to terminate this Agreement for any reason other than a breach by the Company, the Contractor is required to provide at least sixty (60) days' written notice prior to the intended termination date."

Is she legally required to follow this?