Oh she knows about my interest, I don't think she would ever have thought of doing that otherwise. It took a while before she agreed to allow me on her back, she feared she would collapse right away (like most girl fear). Once she tried, she realized it was hard but doable and let's say she "felt" how much I liked it
She's not "into it" but she knows I am so she indulges.
Sometimes when her back is sore from sitting for too long at work she gets before me and hoists me on her back by bending forward. She says the weight on her lower back actually does some good. She only supports me for 30 seconds or so this way but she feels strong and solid, she doesn't struggle. I like that too!