She seems way more interesting than Deacon. I'm surprised she's not a romance option.

Have you played the Railroad questline? There's a good reason she's not a companion.

I just recently joined the Railroad. I don't really care for Deacon and was hoping she might become available to travel with, later in their questline.

Do you really want to know why you can't recruit her?

Play through the Railroad quest line, then you will know.

I'll play through it then since you both say it's explained in the questline. I just thought she was one of those seemingly cool characters Bethesda purposely didn't want to make a companion.