"True," perhaps. "First," most definitely not. She is the first to make him put a ring on her finger as payment for giving it up, so that might say something about the depth of his feelings for her...
Camilla was Charles' first, true and apparently ONLY love, whom he was forbidden to marry, by his overbearing father and he never got over her.
There IS a difference between dating and/or sexual escapades and real, abiding love.