This enemy unit consists of a flying computer monitor accompanied by two wooden angel-like creatures. Although she is above the ground, she does not count as a Floating enemy. Instead, she has only the Witch trait. In this case, she will stand no chance against Witch Killers such as Li'l Madoka, Li'l Homura, or any Uber Rares from the collaboration event.
Despite her enormous DPS, Kirsten has mediocre range and a longer-than-average backswing, making her easy to stall with enough meatshields. As such, she should be a pushover as long as you use Witch Killers or other long range-attacking cats leveled up enough and protect them with smaller cats like the Basic Cat and Tank Cat.