I kept my cool and the visit went on while my mom sulked
Nopuppets, just trying to drop a note since this is your last day and I want to help brainstorm. I think you nailed it with the above response. Great job!
What did your mom want that she didn't get? I'm a fan of organizing activities in a structured way and strategic way. Is there something you can do today that works for everyone that will also address her need to the point that her sulking doesn't impact the entire dynamic on the last day of your visit?
Of course, the bottom line is that she is 100% responsible for sulking. She does it because it elicits a response from you and others that meets her need for love and attention. It's a trigger for many of us and we internalize it, to the point of holding tension in our muscles. If it goes badly today, carry on and keep your cool like you did yesterday. Your girls are watching you and learning how to respond. Focus on that rather than your mom's sulking.
Thinking of you. You've got this.