Give her a chance. Your body learns how to lift these girls.
In the box there is nothing to get you hands around plus you have everything else thats in the box. packaging can also add around 7kg to her weight. By the time that you have that upstairs her actual weight will be forgotten and you will only be thinking of the struggle to get her there.
You're back is probably still recoving!
Out of the box, once you have fully recovered lift with the knee's, not the back.
The girl who seems twinned with a hippo at the moment will seem half her weight in two weeks when you have carried her around a little.
I'm in my sixties, I work in financial IT and the closest I get to a gym is seeing one on TV so not exactly a tonned adonis (much as I'm sure those who attend the iDome will try to disagree with me on that
) but I've got a lot of these girls ranging between 26 and 38kg and happily wander around the house, including going up and downstairs with them.
It does get easier once you learn how to lift them (and every one is a little different).
Just don't overdo it. Give you're back a chance to rest until repeatedly moving her builds up more strength where it needs to be (takes about two weeks to see a real difference and you won't even notice that you are excercising).
Many congrats on your new girl and welcome to the forum,
Shamus.