You obviously want everything to be as close to perfect as you can make it, and would gladly accept help from your worst enemy if it meant seeing her crack that beautiful smile of hers while she tearfully said yes.
People can give you really lame advice and pass it off as the next Apple, or maybe believe it to be that, which is worse. What matters though, is you not being taken in by ideas that could go horribly wrong. Case in point: putting the ring in her drink.
You may have considered this in your youth, wondering how taking a page out of your favorite rom-com would play out in real life. It would probably not work as well as you thought it would. What if she decided to take a picture and post it to Instagram, or choked on the diamond-studded ring if she decided she was too hungry to watch her manners? The latter is not far-fetched, especially since she does not know you plan to propose in the first place.