Beautiful machine and it's in a nice-looking cabinet, too. Bless your mom for taking such good care of it.
Around here, similar machines go for about $25 - $50. Were I selling yours here, I would ask at least $50 because it's pink, its condition is excellent, and it's in a good table. Even if it needs oiling and adjusting, it would fetch at least that. Heck, I might even start it at $100 and drop the price every listing period until someone contacts me.
But I have no idea about the Dallas-FW area.