(sorry if youre not filo and im mistaking you for someone else. "ate" is a term of endearment that means older sister just in case you didnt know)
But regarding your question as to when I knew I was in love w someone, I would say it depends on the person? We prioritize different things in love and I think when the other person basically shows and matches the things we prioritize, that's when I realize like "shit, this person is worth being in love w"? As selfish as it is in my perspective (since it does make me seem more choosy hahaha)
For me, it was all the more clear when my partner stood up for me against his mom. We were in a bad situation then (financially supporting his mom and younger sister) and he had always been a mama's boy and has a hard time saying no. But he still did, for me. It was like he was going against what was the norm for him and what he was used to to protect me and support my side even if siding with his mom would've been the more comfortable choice. It's the fact that he's willing to grow and evolve as a person, a guy who only knew abt computers now knows how to communicate well, cook for me and him as well as even act coy cuz he knows I kinda like them bratty HAHHAHA
But the thing is, those are the things that I like and appreciate and again, I prioritize those things—the being each other's support, being willing to grow and communicate and etc. It might seem cold of me to say this but I found out that I really loved him especially then when I realized—this was a guy I could grow up with. He's lacking in some stuff but he's trying and actually does get better as time goes on. He's nice, kind, passionate about the things he likes and most of all—he's responsible. I might be glazing him a bit much but BASICALLY
I think you know you love someone when your values are about the same, as well as you know their good sides and their flaws but still love and hope for a good life w them anyway and you still look forward to another moment together.
sorry for the ramble but I hope this helps!