In Henry Danger, in the episode "Jasper's Real Girlfriend", Charlotte's bedroom is shown. I was wondering why she has two beds for one person. It could be because she has sleepovers with friends or she shares the room, or she may use both (that show is weird anyway).
Visting my grandparents, I slept in three different bedrooms in their house during different visits, and two of those bedrooms had two beds even though I was the only one sleeping in those rooms when I visited. Over the decades, I slept in about five or six different bedrooms in my family's vacation home, and at least two of them had two beds when I slept alone there. Between the ages of 11 & 18, I slept in a bunk bed, and I remember only one visitor ever using the top bunk during a short visit.
So I think is possible that Charlotte could have been the only person who slept in her two-bed bedroom. Or she might have shared her bedroom with a sibling - considering her age, I would hope a sister and not a brother.
And I don't remember any mention of whether Charlotte had any siblings in any episode.
Maybe she has a sibling. Maybe her sibling died, or is grown up, in the military, or dropped off the face of the Earth. Maybe she does and doesn't tell Henry nor Jasper about her becuase she did something to her, and her family, and doesn't want to talk about it.
Or maybe the bed is in her room for Plot Convivence. Who knows.