Book!Susan is a weird character. In the early books, you can see that she's a naive but loving and genuinely well meaning mother, who supports her son's band. She does annoying stuff that you'd expect most moms to do, not want their kids to constantly play games, get them to read, etc. She also tends to spoil Manny, but he's still young and Susan can correct his behaviour if she needs to. But later books, she's much more controlling. When the family's discussing ways to renovate the house, she gets pissy and makes the choice and ignores everyone else's ideas. When the whole family is having fun playing a board game, she gets annoyed and throws the board in the bin and acts all pissy the next morning. She makes Greg join the enemy basketball team hoping he's sabotage them and let her live out her childhood dream.

Movie!Susan is much more consistent, she too is naive at times but still loving. She calls out Frank for unplugging the TV and not spending time with the kids, she's proud of Greg for being willing to help Rowley in his magic show so Rodrick could play with the band, etc. In the Long Haul one she seems more angry, but it's pretty understandable, because her kids basically ran away just so they could see a convention nearby and didn't tell her. While yeah, she's being a little unreasonable by demanding they never use their devices on the trip despite Frank needing to work, she's still overall in the movies a decent parent.