You gotta give a bit more info then that like how far have you progressed with her or what are her LP at, was a while since I played seeing as I decided to wait for the lag to be gone and I just tested and it's still there so gonna keep not playing it
![Big grin :D :D](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
.
First of you need at least 25 LP to ask for a date with most of the girls, this applies to Shiori, but since you went on a date I'm guessing it's over that.
After this each time you do a date with 100% you get a "chance" to take them home for sex, however if it's to early or the weekend they will ask to move to another place first, agree to this and then try to leave again to have a chance at sex. The more LP you have the higher the chance of them to agree to sex after a date.
For most of them you still have to get enough LP or progress far enough for them to agree to sex. I might be wrong on this but I believe you must have done the babysitting part with Shiori to sleep with her, I might be wrong on this since again it was a while since I played last. You might have also just gotten unlucky that time and not gotten the sex offer.