AITA for telling my best friend she has to lose weight?

I created this throwaway just today because I don't want her to find this post. I'll keep it minimalist.

I've been friends with this person for over 10 years starting when we were very young, probably 7 or 8. I've always been a bit heavier than my other friends, but that doesn't say much when most of my other friends are dancers and athletes. In fact, we've both always been usually the heavier people in the group until about 2 or 3 years ago when I lost 15 pounds and my BMI became around a 20. She was now the "odd one out" when it came to weight.

I recently entered a relationship while my friend has been pining for someone for a while. One day, she just straight out asked me, "Why doesn't anyone like me?" I explained that it wasn't her, it was them, and that being in a relationship should not define you. I thought it was the end of that. Turns out that instead, she became depressed and gained 25 pounds. She was now obese. I supported her until she got better, but her complaining just continued.

Recently, she's been trying to find clothes that she can wear to a party, complaining that everywhere she goes, nothing is in her size. One day, I got fed up and told her, "Maybe you should try going on a diet or something." She didn't take this lightly and accused me of calling her fat. I told her, straight, that maybe it wouldn't hurt to lose a few pounds so that she has something to wear, but she didn't listen and has since then ghosted me.

Am I in the wrong?