The Garner/Walter/Bedford storyline is definitely the weakest subplot in the movie though it would be repeated in real-life many years later by I think Didier Pironi and a fellow driver the year that he was injured out of F-1.
I think it's because she is of two minds: a part of her is very much in love with Stoddard. Another part of her is very turned on by the thrill of being with a man that has such a dangerous profession.
When she's with Stoddard, those 2 feelings can't be reconciled, so she leaves him. With Aron, because she doesn't care for him the same way she does Stoddard, she can be free to feel the thrill again.
In the end, her love for Stoddard wins out, and she had to find her own way to deal with the possibility of losing Stoddard forever. This is something that comes up a lot when reading biographies of 60's and 70's F1 drivers and their home lives.
Pat was opposed in principle to the danger her husband was in, but the real problem was, Scott was too absorbed in his work and was neglecting her. It wasn't about racing. It was about his ignoring her. When Scott realized he could lose her, he got over some of his obsessiveness and began to treat her with more respect. He realized, a living wife is better than a dead brother. Clever Pat. Pete just happened to be in the right place at the right time, so to speak. I think the scene where Scott says "thank you" to Pat is very touching.
I really do believe she hated him racing and feared for her husbands life because he was chasing after the ghost of his brother. So his reasons for racing were actually in itself dangerous. Aron did not race for those reasons so I am sure she did not fear for his his life every time he got in a car for a race. Remember she saw the agony Scot went through chasing his dead brothers record. He would stay up the night before a race in terror. So she probably liked car racing but just did not want her husband racing, because of that monkey he had on his back about his dead brother. Something Aron did not have. I can actually understand her.