What is the evidence for love?

I made a YouTube video to re-enact a lame conversation that I may or may not have been involved in.
I'd be interested if this sounds like the sort of conversation you've ever had, and how you'd finish it.
It's probably as much to do about lack of critical thought/reason/rationality as it is about belief and religion.

https://www.youtube.com/watch?v=37UQEMSqyA8

There are measurable biological effects of "love". There is absolutely scientific evidence that it is a real thing. If your friend is talking about love as something that exists outside of the person who experiences it, caused by something other than chemical reactions in the body, then simply reply that she is correct that you don't believe in it.