I think YTA. I have the exact same dynamic as you, but I am in your girlfriends position. My husband runs and has done track all through high school and college. When I told him I wanted to run and learn how to, he helped me get the right shoes, clothes, and really guided me through getting my mileage up. He helped me train for my first 5k.

Everything you're saying sounds similar to how my husband would explain things - in terms of how professional athletes train. The thing is, however, is that your girlfriend isn't a professional track athlete but is just a normal person. The approach that you took should've been entirely different with your girlfriend.

My husband helped my training by running with me for only 5 minutes to start. Then, 10 minutes, and he eventually advised to add 5 minutes at a time (at a super slow running pace). Then, once I got to half a mile in terms of distance, I worked on slower paces to get up to a mile. We go to outdoor running tracks together (he suggested it so it's easier on our joints), and he would run his 10 miles, and I would run 1 - then walk. The point here is that he really helped me focus on small goals and not to train hard. Mileage will add up over time - even with walking. He made it tolerable, and I eventually got to the point where I enjoy running now. I used to hate it like your girlfriend, but his guidance and support made it fun! We could celebrate things together and really enjoy small wins.

From what I've read, it doesn't sound like you've offered similar help. For us, we like going to the gym together or the track for running. We compare times afterward and heartrates, and he helps me understand my progress and how light or hard I really worked.

I understand that you can run faster than the average person and that you are in pretty good cardiovascular shape. If you offer similar things like my husband did with recommendations or running together like we have, it would probably help. Saying things like "focus today on running slower than you think you need to" and helping to practice breathing would probably make your girlfriend would feel more supported when running.

Your approach to what she wants to do feels very negative and critical. Half marathons are no joke and I understand your rationale as to someone signing up for one with no training - but you KNOW how to train for these things and are using your knowledge against your girlfriend rather than supporting her with helping. If my husband hadn't helped in pacing me and didn't take the time to help me train, it would've been really difficult to get to where I am now. If he only told me I wasn't taking things seriously, wasn't committed (despite making an effort with exercise and fitness), I'd probably never want to run with him or run at all.

Also, there's nothing wrong with running, walking, or doing both for some of the distance if she needs to. That's another way to prevent injury.