You can beat Lily by finding a specific hiding spot, look for a door to a room that you have likely never entered. In the room, there is a fridge, a table, etc. But also a little hiding spot, that you can block off.
The beating her with the power off is not yet a concern. To beat her, you need to first hide in the spot, then when she starts patrolling, you need to make it back to the chair. This part is much easier to play with headphones, as Lily's singing helps you with the direction she's heading in.
I am sorry that the jumpscare hurts your eyes. The disclamer states that the game has flashing lights, although most jumpscares do not use flashing lights, but rather zooms and camera shake. I am assuming that you ment to say that it hurts your EARS, which I can totally understand. If your master volume is at 6%, try to also lower the "Other" volume category. This includes the jumpscare sounds.
TL;DR, find a hiding spot that is in the kitchen room, wait for Lily to leave your hiding place, catch the right time and sprint back to the chair!