- “This was a good breakfast, Beth. You really made the crap out of those eggs. I wish your mother was here to eat them.”
- —Rick referring to his wife.[src]
In the pilot episode, the first mention of Mrs. Sanchez happens, when Rick says "This was a good breakfast, Beth. You really made the crap out of those eggs. I wish your mother was here to eat them." This comment was so nice, it brought a tear to Beth's eye.
It is hinted by the scene from the pilot, that Rick's wife is deceased, but this is dissolved in Rick Potion #9, when Beth reveals that Rick left his wife, as well as Rick saying that "Love is just a chemical reaction that compels animals to breed" before mentioning that he was also part of a failing marriage, much like his daughter and son-in-law. He then encourages Morty to break the cycle and focus on science.
In Auto Erotic Assimilation, Beth tells Rick that "I can't sacrifice this whole family's safety just because I'm afraid you'll leave again," noting that in saying this she sounds like her mother. This seems to indicate that Rick left his wife because he placed the importance of his experiments over the safety of his family. It's possible that she is still alive but doesn't come around much and it's still possible she might make an appearance in the show.
In The Rickshank Rickdemption, Cornvelious Daniel, an agent from the Galactic Federation, went into Rick's memories, via a brain-link, to retrieve the origin story of Rick becoming a criminal. He found the memory of Diane Sanchez, who was clearly the wife of Rick and biological mother of Beth. A bomb portalled in from another dimension (suggesting it came from the other Rick previously seen in the flashback) explodes, vaporizing both Diane and Beth. However, instantly after this, Rick revealed that this whole story was a completely fabricated story he quickly thought up, just to trick Cornvelious Daniel into giving the Brainalizer a virus, making it unlikely that Mrs. Sanchez was the woman, portrayed in the story.