I really really like going to my sessions alone. I like being focused on the experience and on connecting with the artist too. I know some artists don't mind having you bring a companion but I also don't want to be worrying about anyone else—if they're okay, are they getting bored, are they hungry—while I'm getting tattooed. (Unless we're both getting tattooed.)
My brother went with me one time but that was a really quick session (less than an hour) and the two of us had fun chatting with the artist while she worked.
My aunt who was hosting me in Seattle arrived too early to pick me up after my appointment and she soon got bored so she and her husband left to have dinner while I was finishing up (it was a 9-hour session).
One time, two travel companions insisted on walking me to the tattoo studio in Denmark. I told them they can say hi to the artist but that they wouldn't be allowed in the tattooing area. So they did that, gushed over his design, and left.
Then again it might be a different scenario if you're talking about a person you really really like. Maybe weigh if having her there for the entire five hours would make the experience better for you?
Otherwise, maybe you can ask her to drop by when the session is close to being done.