I do her two ways depending on my spec:
BM - Send in pet, NR aspect, autoshot, and purely mend pet between boulder toss. If you have Hawk Eye it makes it easier to stand in range of the pet but out of range of the AOE. I did this in blues so it's doable, but easier once you have GS set bonuses.
MM - Cheetah on, send in pet, nuke her at start then start running once she aggros you. Pull pet off her and keep it at your side. DON'T use multi unless you want to clear the turtles first. Keep running and she should boulder toss the pet mostly. When she stops to AOE, turn and auto/aimed/auto her then keep running. You can also jump auto shot her during running. If she does boulder you, you'll get stun and daze. She tends to AOE a lot though so there's a good chance you can walk it off. If not, FD and let pet re-take aggro, and keep running.
If you want to farm all Princess-side bosses, I'd recommend BM since Rotgrip tends to be a pain. I farmed around 1000g in a week like this, it's really much easier as BM and you can afk a lot more.
You can see the vid I made for optimal trash timing, although it didn't record my Princess kills:
https://www.youtube.com/watch?v=hl4Zp_MevPg
Nostalrused...