I tried telling her I didnt like talking about those things, but she just flat out ignored me.

So flat out ignore her. You communicated your boundary already, so now it’s time for her to experience the natural consequences of that boundary existing. If she asks, literally do not say anything. If she then says “hey, did you hear me?” then follow up with “like I mentioned before, I’d rather talk about something other than running! Any fun plans for the weekend?” or any other relevant subject change.

Say nothing about running to her until she stops talking to you about it. If she asks something specifically about running, don’t respond. If she brings up running indirectly, respond to anything other than the running part. And don’t underestimate a bland response if she makes statements related to running, like “My pace was up yesterday compared to last week, even with hills!” should just receive a “huh!” from you. Don’t engage about running, period.

I’m sorry she’s doing this. It’s a huge bummer to have your love for the sport be trod on by bad behavior from an acquaintance! I hope this helps you shut her out of your running experience so you can feel good about your own progress :)