Just ask... see where that takes you. Do you want to because you like the "feel" of the satin/silk/polyester? If that is part of it, and she isn't receptive to you wearing hers, purchase some of those sexy silky boxers.

__________________
A blessed thing it is for any man or woman to have a friend, one human soul whom we can trust utterly, who knows the best and worst of us, and who loves us in spite of all our faults.