No heres what you do....

buy one of those gold dipped roses from www.ihatestevensinger.com and give it to her on valentines day when she first wakes up... tell her something like "this rose will last forever" pause a second to let it sink in, than BAM, follow up with the ring saying "and so will my love for you".

Guaranteed yes, plus if you dont waste time, you should still be rocking a morning hardon and have the best sex of your life right there.