Here's my story, FWIW...
I was in a very similar situation for a number of years. I was good friends with HighSchoolFriend, and then I went out of state for college. When I eventually moved back to where we grew up, she introduced me to all her college friends. Most were nice, but one couple was exactly like this. JerkWoman seemed to want HighSchoolFriend to be her best friend, but that position was already occupied by me. HighSchoolFriend and I were MOHs in each others weddings. That just made JerkWoman even meaner to me. JerkWoman did everything she could to divide HighSchoolFriend and me, and I just ignored JerkWoman and her husband, JerkMan. They treated my DH the same way.
After years of this, one time, I did mention JerkWoman's behavior to HighSchoolFriend's husband and he must have had a talk with her because she came up to me and faked niceness. Just the one time. And then she went back to how she'd been before.
I couldn't figure out how HighSchoolFriend had not noticed it before. I know I would never let any guest in my house be rude to another guest. There were plenty of awkward scenarios like OP described. If I followed up with a question like "What kind of cars are you looking at?" JerkWoman would just say in a rude tone "I don't know" and then start talking to someone else about something else, so it was just more insulting. There was no point in trying.
Eventually, it became like a tug of war. JerkWoman was trying to claim her territory and claim HighSchoolFriend as her best friend. HighSchoolFriend seemed to enjoy the attention and seemed to want me to compete with JerkWoman for her friendship. It even seemed like she might be pitting us against one another. For a lot longer than I should have, I put up with it, out of reverence for the years of friendship that HighSchoolFriend and I had had.
But after attending numerous events at HighSchoolFriend's house where JerkWoman was mean and HighSchoolFriend didn't react to it and even seemed to enjoy it, I decided to let JerkWoman have her. I remember telling DH that it's not like HighSchoolFriend is a romantic interest where you can only be in a relationship with one other person. I'm fine with her having numerous friends, but apparently JerkWoman didn't feel that way and HighSchoolFriend was ok allowing rude behavior in her home. More and more, these events made me uncomfortable. It's so counter to my nature to walk into a room and not greet everyone or look through someone as if they're not there. That's what I had to do to handle JerkWoman and JerkMan. I felt like I was going to a snake pit every time there was an event. I was either ignoring, faking that I wasn't uncomfortable, or waiting for rudeness on JerkWoman and JerkMan's parts.
I decided that JerkWoman could win. She could have HighSchoolFriend. There's more to the story, of course. I didn't want to see it, but I finally had to accept the conclusion that anyone who would be friends with someone like JerkWoman was cut from the same cloth. HighSchoolFriend is not any classier than JerkWoman and so I gave her the cut direct.
I'm glad that I've distanced myself from that situation. I wish I had done it sooner.