To "love sth or sb to bits" is an idiom which simply means to love a lot. It does not have to refer to romantic love. It's an old idiom and I don't hear ot a lot anymore.

I don't think there is a general agreement on what Love you to bits means. Bits in English is usually used as small pieces. Loving someone to bits means that you love them so much that loving them in their entirety is not enough, you need more to love and therefore start breaking them down into many bits and pieces so you can devote your love to each piece individually thus increasing the focus and passion. I am not sure this will make a lot of sense to you but then again in any language love makes little sense to any of us in good or bad times. which is why it is so enduring and important i suppose.

Ok, think about this: if you tell that to a friend it would sound really really sweet because it means you love this friend a lot, more than you usually love a friend.. but.. if you use that expression with your girlfriend, it would sound just too casual... at least for my taste ! Ex : Full moon, lots of stars, you and your "other half" (haha) are there, at some romantic place watching the wonderful night and you say " I LOVE YOU TO BITS " ... I'm sorry, but, as your girlfriend, I'd change my face dramatically into this look right here: O.o ^^