I bet she had more screen time that was cut but honestly I think she was put there to establish a character who’ll get more screen time in later installments.
This is more than likely the biggest reason she’s even still in the film (even though most of her part in it could easily have been done by PlasticSoldier93730). We’ll see Phasma again, probably pissed off and with an ax to grind.
And there WERE so many great characters! I can’t sing enough praises for Finn. I admire his courage; he looks at some pretty tough situations and jumps in head first. Grabbing a lightsaber and going after Kylo, no questions asked? Just another day in the life of Finn. He’s got real potential. Plus I love how he plays off of both Rey and Poe. The three of them have real on screen chemistry, almost more so than Ford, Fisher, and Hamill did in ANH (blasphemy, right?!).