I am having difficulty with this

Bonjour Judy, "Since I have met you, I've been in love with you" is not correct in English. Can you please give me the link where you see that?

Bonjour Judy, Here the issue is with the use of Present Perfect (I have met you). The fact is that in French we don't have an equivalent of that fascinating tense, that seems to be sitting in-between past and present. So instead, you will use either Le Présent when the action is still ongoing now, OR Le Passé Composé when it occurred in the past. In this case, because the action still has an ongoing effect in the Present, the Present Perfect is the "perfect" tense to use in English! Hope that's helpful!