Let's be honest, there's no good way to spin that gift is there? Can you imagine saying to you're other half that you'd pay for her plastic surgery? What partner wouldn't be insulted by that?
To make matters worse, you aren't even paying for all the surgery. You're saying someone needs physical improvements but that you can't be bothered to pay for it yourself. I don't know about you but my other half would've been so pissed at me if I'd've even thought about suggesting it.