like the rest you should 'talk someone into' something like this.

i think your best bet is to get her relaxed and do exactly what tbone says - least thats what i would do

make sure she's comfortable enough to enjoy it though - u want her to assocaite anal stimulation w/ a good feeling not an uncomfortable one

work up to it slowly - and i know this has probably been said on every anal thread thus far - but there's no such thing as too much lube