How about just insisting that she recognizes that your feelings are just as important as her bodily comfort at the moment. What's wrong with giving you a quick kiss and saying "I'm sorry. It's just too hot to snuggle tonight.". She can enforce her boundaries in ways that are affectionate and polite rather than ways that are brusque and rude. As another example, my D has always been a super-snuggler and for years she would cuddle on the couch with me in the evening. Sometimes I would find this physically uncomfortable (hot, too much weight, cramped legs etc.) but I would never boot her off the sofa without saying something like "I love you snugglepuff but I really need to stretch my legs.". I cared too much about her feelings to be less kind.
"Tell me, what is it you plan to do with your one wild and precious life?" - Mary Oliver
