mccollum1, your profile says Mom has mobility problems. No, I've never heard of that causing spitting.
If you've told us that your mother has dementia, sorry I missed that. Fluid accumulating in the mouth resulting in drooling/spitting is often a symptom of dementia. Talk to her doctor about this.
What exactly do you mean by spitting? Spitting at people in frustration/anger? Spitting and sputtering when eating? (such as Pamstegma refers to) Spitting out food that she has pocketed in her cheek or discovered below her dentures? (this is something my mother does... sigh)
If you've told us that your mother has dementia, sorry I missed that. Fluid accumulating in the mouth resulting in drooling/spitting is often a symptom of dementia. Talk to her doctor about this.