The rubbing out - maybe encourage her to cross it out. Some children will spend more time rubbing out than working and having to do it all over again can be frustrating.
Homework - if it is causing stress put it down and walk away. Especially if she has understood the concept. You can write a note to the teacher to explain so she doesn't get into trouble.

How about asking some of the children over for playdates. One at a time so she can get to know them.