Summer before sophmore year in college, I hurt my knee and was prescribed Darvon for it. I had signed up for a Modern Dance class in the fall and hurt it worse. Came home from the class in a lot of pain and took 2 and went to sleep, kept waking up and taking more, and ended up taking too many in too short of time.
My roommate came in and opened a jar of peanut butter.
The smell of the peanut butter was all it took to make me sick.....so sick I ended up having to go the Student Health, admitting to how many Darvon I took, and spent an hour trying to convince them I was in pain....not suicidal.
Upshot was.....I had to drop dance class, had physical therapy for 2 months, have never been able to take even one Darvon since....and if I am the least bit queasy for any reason and smell peanuts or peanut butter - I will be 
for hours. If I have the stomach flu....just seeing a peanut butter commercial on tv will do me in.
Wild guess Frank....you must have gotten very sick when you were very young...that while it might not have had anything to do with the animal fat, you probably had some steak or hamburger prior to becoming ill. Your subconscious puts the two together, triggering an automatic response to the smell of animal fat.
Chances are, after all these years...it isn't going to ever go away. And since you had such a strong response the other night, you might have been getting just a wee bit sick even before you smelled it....
I agree with Debk on her wild guess.
I had a bad experience years ago when I had a stove fire in my kitchen, hot oil spilled or should I say exploded oil over my legs. 3 rd degree burns on my legs, 16 % of my body burned and still steaming by the time I got to the hospital.
For years I could not go into a fast food restaurant because of the smell of the french fries cooked in boiling hot oil.
I can not to this day forget the smell of burning flesh, human, mine when I smell rancid fat.
The 4 years I spent as a vegetarian almost did me in, after a year or so of no flesh except liquid ( EGGS ) and milk products I could walk into a supermarket and if there was any spoiled chicken or meat I could pick up the Oder at the door. County fairs were awful,, I could smell rancid oil the vender's were using to cook what ever food they sold.
My turning point was at the mall, there was a new steak house just inside the door. When I entered and walked past and smelled the char broiled steaks, I broke,
just had to have one, right now, medium rare with all the fat crisped up and enough juice to run down my chin.
Funny, when I began to scarf down meat my problem with deep fat fried anything went away. I even took a part time job at a burger joint and was able to cook the fries with no problem. WIERD.
Frank, We know now that smell is so important a part of our lives. The smell of baking bread, roasting Turkey and stuffing, can you smell the air and tell when it is going to rain or snow.? Early morning camping out by a lake and somewhere someone is cooking Bacon and eggs on a grill, coffee perking in an old fashion grill top pot.
What about pork fat and Bacon, Frank, is it just beef or can you handle other kinds of fat smells ?
Woman's perfume, ever run into a woman wearing a perfume you have not smelled in years.? An unexpected smell that sends your mind back to either a wonderful memory of a really bad on.?
I think Debk is on to something here, You may well have begun to come down with some ailment and the smell of beef fat and some buried memory of an unpleasant experience may have just added to the problem.
Patchouli for some reason really annoys some woman, I like the smell, Hubby has no problem with it but both my daughters will leave my house if I have incense burning, who knows I may have been wearing it when I had to give them some really bad news when they were kids.
As for your reaction to just the smell of beef fat, usually we tend to crave the food that is worse for us, or perhaps lacking in our diet.
My advice is to just let it go, if the smell of something annoys you stay away from it.
BTW, the worse smell for me today is a potato gone bad, To me the smell reminds me of funeral flowers that have been next to the deceased for 3 days and the body was not embalmed.-----Home funerals where if a man , the undertaker came in every day to shave their face, no the hair was not still growing, the skin was shrinking and exposing the hair.
Perhaps the Scientologests have stumbled on a reason on why we humans get the Willy Was for some things, all this may be way back in our subconscious going back before birth or shortly after.
Very elaborate our brain, very venerable to outside forces, everyone is different, WHY.?
In the world of other then human one can study plants and animal's and know what to expect. In us humans it is a crap shoot, genetics plays a role but so do outside forces.
For you Frank to ask why you have a problem with beef fat is akin to asking why people fall in love, why some people are good and some evil.
When people around me are gulping down live Oysters on the half shell I tell them I am allergic to Oysters, not a lie, my brain is allergic to eating anything living. So you need to let people know that you in some way are allergic to beef fat, and not spend one minute worrying about them or what they may think.
Some things are are as they are, the color of your eyes, your delight eating Brussels sprouts, you're taste in woman to your favorite color. It is just YOU, no one else is like you, expect those around you to not understand, that is their problem.
You did right by eating the middle of the steak, but why worry about it, you used tact and and observed the decorum for that feast.
Remember-------Jack Sprat could eat no meat, his wife could eat no bone, so between the two them, they licked the platter clean.
