if you think that sex is on your mind one night could you maybe make her a cup of coffee that night or if she likes a little wine or mixed drink (my husband when he gives me the hint hes in the mood will hand me a high ball glass of jagermiester and pepsi
lol )
maybe that little *spike* will give her just enough energy to stay *UP* with you
i know some people are against "planning" sex but maybe you could wait til friday night or saturday night when she has time to relax a little more during the day so she'll be up at night.