Is this like a boy's handwriting or a girl's handwriting?

According to the font and handwriting in your photo, there is a 90% chance that it was written by a girl.

Girls' fonts are generally petite, and the fonts are clearly written, not very sloppy. It's not very nice, but it's clean.

Boys write badly, even the ugly 1 is scrawled and not very neat. It may have been altered, so it should have been written by a girl.