My parents were married for 32 yrs, during the marriage my dad built a house, but my mom decided to leave my dad, what right does she have?

Yes. In Texas, when a couple divorces, all property they have is considered community property unless it was acquired by gift, by a Will or by inheritance. In this situation, your mom and dad were married when they built the house. The house and all other property they acquired would be subject to being divided in a divorce. Common law marriage is treated the same as ceremonial marriage in Texas in that the couple would need to get a formal divorce before they could marry someone else.