Pure strength and athleticism allow a person to avoid being put in that scenario. No way a 6'1, 165 lbs. guy is going to physically be able to get a very strong and athletic 6'2, 230 lbs. guy in that type of situation. It is why MMA has weight classes, because they know that technique and specialty can only be of value to a certain extent, but with extreme differences, it can't make up for sheer strength and size differences. If not, they would have no problem with a 250 lbs. guy going against a 160 lbs. guy.
For three years, I had an ongoing argument with my senior managers. About eight of them were adamant that Ronda Rousey would kick my ass. I argued that the sheer size and strength differences and male/female dynamic would be far too much for her to overcome. The only two people who sided with me were a former UNC track star (who was on the same team as multiple Olympians) and a 36 year old guy who regularly travels and competes all over the Northeast and Mid-Atlantic in jiu-jitsu. Even though he is trained at a high-level, he knows that there is no amount that can overcome that large of a disparity in size/strength.
Except Jiu Jitsu (which is the majority of the fighting you see in UFC) has open weight/absolute divisions, where athletes of varying weights/sizes compete against one another...and in many, many cases, the smaller sized guy won. It's considered to be THE testament of who's the best at a tournament because you're taking all the belts of a certain rank and saying, "All y'all fight and see who's best" AKA Absolute Champion.
A more recent example was "Mighty Mouse" Demetrious Johnson submitting a man far larger/heavier than he is...and it was the finals of the Pan games, meaning his opponent was no slouch:
This is of course in Gi, and there is no Gi, the latter being more popular as it resembles wrestling/grappling.
But the smaller man can win. Athleticism sort of isn't always universally defined:
As I said, hyper-extension is a much smaller amount to get someone to submit with. A 15yr old girl with 5 years of training can/has submitted a full grown man with less experience...
Hell, Royce Gracie's UFC run pretty much showed you can beat athletes with technique.
In the case with you and Rousey? If it's just you, as you are, and she as she is, you'll struggle for quite a bit but ultimately win if you can knock her out or get any kind of submission (assuming you can properly apply any) and it would be an ugly win.
If it's strictly BJJ in the Gi? You're gonna really struggle since the Gi is a weapon and she can literally choke you out with the cuff of her sleeve.
I will also say, women's weight in BJJ has less divisions at times, and women are often paired based on experience level instead of weight. While she may not routinely go against a 220lb woman, she likely is used to heavier opponents in general.
However, one thing about Rousey, her sport is Judo and always has been. If it were Judo? She's absolutely the favorite as she's Olympic level and she'd only need a throw to win.
Athleticism can work against you if you're untrained, since you're wanting to use your speed and athleticism to get out of, say, a Heel Hook, and you turn the wrong way? A bomb just went off in your knee and there's a high probability you'll never walk the same again.
