Maybe the girls and her mom are still at the WH so she stayed there. I just like it when they get to get away together, even if it is for him to mostly do WH work.
The President's dad and mom, and Laura's mom went to church with them. So you're probably right. Laura's at the White House with family and the animals.
If "I" were first lady, I would have come home from church, put my flannels on, given the servants the day off, and read a book/snoozed all day. I'd just have to catch up after all the fun.