I assume she's competing in TPOT since she has the Yoylite with her, which is the only season where she got to wield it.
Anyways, to explain what Pillow does, like every other contestant in the series, she's most prone to leading with whatever piece of equipment she has on her that is the most effective thing to use. In this case,
she's able to use her flamethrower to spam rapid amounts of fireball danmaku per shot, and since she has the Yoylite with her, she could have the potential to go back in time to either an earlier point in the fight where she can try again or straight up kill a younger version of Vegeta if she wanted to (Probably not likely since she'd have to find a younger version of someone she hardly knows anything about, but it's still possible). Plus, if she dies while having the Yoylite on her, she ends up gaining Immortality Type 6 that will allow her to resurrect herself at the Recovery Center without the need of anyone to recover her, where she could then use the bracelet to return to the fight.
Speaking which, how far away is the Recovery Center from Pillow by the time the fight starts? Because throughout TPOT, its location changes thanks to it being moveable.