7 year old girls

Olivia

Ok so my boyfriend has 3 kids. 14, 10 and 7. The other two listen no problem or anything but the 7 year old has an attitude from hell and it’s only when she comes back from her mothers. I’m ready to knock her out with this attitude she has. Anyone have any tips or ideas on how to get rid of this attitude cause I really can’t handle it anymore.??? Please help