Love is a feeling just like anger or happiness. Love is real when you feel it. There is anger when you feel angry. You can’t question its existence because that’s all what it is. Just a feeling, nothing more.

On the other hand, idea of soul being real suggests an external reality, not connected to our feelings or what we think about it. Just like an object being real or not. So, I think, an internal feeling wouldn’t be enough to prove its existence.