Okay, so Mrs. van Daan isn't actually a scout leader. But she's as protective as a mama bear when it comes to her precious baby boy. And later, she nurtures Anne quite a bit, especially during the periods of time that Anne doesn't feel like confiding in her own mom.
Mrs. van Daan—whose historical name is Auguste van Pels—is one person that Anne can’t stand. She’s belligerent and selfish, always instigates fights, is rarely helpful...
For the umpteenth time, Mrs. van Daan is sulking. She’s very moody and has been removing more and more of her belongings and locking them up. It’s too bad Mother doesn’t repay every van Daan "disappearing act" with a Frank "disappearing act." (9/27/1942.4)
... and her character doesn't seem to change over time.
She's also jealous of Anne’s relationship with her son, wanting Peter to confide in her rather than in Anne.
However, Mrs. van Daan does have a few strong points. She occasionally can be reasonable and back down from fights, is generally neat and tidy, and is often easier for Anne to approach than her own mother.