Say..: "Nothing can prove how much I love/like you. It's difficult, because you need perfection. I can't give you proof, so you must take my word for it."
Say you'd murder someone for her or send a picture of your dick//ria: JUST SAY "I don't need to prove it cuz I love you to much UwU" or "your like a sun in my life I can't live without you"