I live in an apartment building, on the top (6th) floor. I have knobs on the radiators to adjust a bit, but ultimately I do not control the heat. I cannot turn the radiators completely off.
My apartment is always always above 75f. I know this because coconut oil is always liquid in my home. Often in the winter its much hotter then that, sometimes very uncomfortably so. I keep windows open, and if it gets too bad I will blast my a/c and while both help, its always above 75 in my home. There are some drafts, which are welcomed.
But ultimately guests need to simply dress appropriately. its warm, it is what it is. Its not an unhealthy temperature, its just warm.
Your host obviously has some reason the home is that temperature, either by choice or circumstance. But its probably something she is accustomed to. I think 79 is warm but not unbearable, so I think you should just dress appropriately and keep drinking water.
ETA: I live in NYC, where winter weather ranges from the 40's down to the 20's or 10's. This has been a warm winter in mostly the 30's, but even during cold, below freezing outside, in fact especially when its super cold out, my apartment is warm to hot.