Party Rose is a joke. While Party Corn and Citron can carry their own weight, she is just close to useless. 8 damage and 18 shots doesn't do anything; barely helps in Ops.
It's as if Popcap wanted to give us all a good laugh while regular Rose simply deals triple the amount of damage before she has to reload.
If anything Party Rose needs a damage and her clip size has to be increased.
Lets put this into numbers:
Regular Rose: 10 damage x 30 shots = 300 damage per clip max
Party Rose: 8 damage (12 buffed) x 18 shots = 144 (216 buffed) damage per clip max
So even with her party mode active she still deals less damage. And since half of her shots will miss anyways nothing will be defeated before she has to reload.
9 (12) x 30 would be acceptable.
And all of that doesn't even take into account the problems of party meter.