It's the only thing I dislike about cycling other than that events start soooo early in the morning; all the *&^% sorting. "I ride 30-40 miles brisk pace, you like 50 - 60 miles dizzyingly fast pace on the flats, she's riding 20 miles slow but loooooves hills ...." Can we ride together? Mmmmaybe, maybe not.

Options could include but are not limited to ;
you bring beater/errand/fixed gear bikes she brings road bike.
do a spin class together.
cross train together.
do the same ride, she rides her pace you do hill repeats*
find a local club with tiers. Meet at start/finish/recovery meal

*there's a possibility of her feeling bad as you do the hill 5 times as she rides up it once but whatever. As long as she's training she will get there too. You encourage and inspire her and sip a recovery beverage as you wait at the top.