The fact that she’s trying to pivot and weight shift to play with toys is very positive.
Using your leg and pillows to prop her up to encourage more weightbearing through extended arms is right on track.
You can also try moving toys towards her preferred side while she’s in tummy time so she pivots in that direction-she’ll have to push off the floor more with her non preferred arm to get there. Does that make sense to you?
When she’s playing with the toys, try to encourage her to play with her preferred arm so she’s weightbearing more on her non preferred arm. And then switch so she’s building up strength symmetrically.
When she’s lying over your leg, try lifting her legs off the ground so she’s forced to weightbare until she fatigues and can’t hold anymore.
If you’re not seeing progress symmetrically in the next few weeks, it’d be worth an extra look. I’m happy to set up a consultation if you feel it’s necessary.