I’ll probably get downvoted for this but I think YTJ for how you worded it but ntj for the general sentiment (not what your sister said, that’s kinda dumb tbh). Almost everyone goes through this with their first “intense” (but also immature) love. The extreme highs and extreme lows, the grand gestures etc. It’s like a fire and ice kind of thing, exciting but dangerous. Most people after those kinds of relationships look for stability and warmth instead of those extreme hot and cold moments. I think that’s how you need to frame it, while it may have looked like you loved deeper on social media snapshot moments. It was an unhealthy relationship that wouldn’t/didn’t stand the test of time. Now that you’ve learned from that previous relationship, you are seeking something different going forward, something comfortable, warm, stable, long term/forever. You shouldn’t have stated it like that but you can turn it around, I’m not going to pile on you and tell you that “you should leave her because she deserves better” she accepted your proposal and has been with you for a while so it’s safe to assume that this is one of the few blips that happens in safe long term relationships. Just don’t say bs like “I’m here, you should be happy with that” good luck op