Either way works and we have done both. Do what is best for you, Damn what anybody thinks.
Mike

Without reading any further, I agree with Mike!

I spent most of my life riding two up and I think I've experienced just about all of it......so just a couple tips to consider......
If you're going to get on first, as she swings her leg behind your backrest (assuming she gets on from the left....the low side), you can reach back with your right hand and just kind of cup the bottom back of her heel. It's awkward for both of you at first but it will become normal for both of you if you keep doing it.
If she gets on first, there's two variations, depending on her height. Assuming your parked on solid surface (the only time I'd let her get on first) and she's getting on from the left side (low side), if she's short.... she backs up to the bike and with her left foot, steps up on the passenger floorboard. As her body rises, she's shifting her but back and down into the seat...then she swings her right foot over your backrest (usually folded forwarded). If she's taller, she may not need to step up on the floor board....just back up to the bike and put her butt in the passenger seat and slide back, before swinging the right leg over.
One thing that she has to be careful of in this approach is to not lower her foot so low that she hits your tank or tank console.
Just experment and figure out what works for you two. What ever it is, it'll probably feel awkward at first but you'll both adjust with repeation.
