The gist of what I remember is that a girl desides to dress up as a sex doll for her significant other. She also has two other dolls for him to play with so that he doesn't "know" which one is his girlfriend.
Hi
With there being so many doll stories
Look in Gromets Doll section first.
Read the description first to see if anything rings a bell
Please try to remember more about the story
It will help to find it. A person , place, or thing
might pin it down,
Goodluck
That should be
I 'm his Dolly by Gromet.
https://www.dollstories.net/storiesek/imhisdolly.html
https://www.dollstories.net/storiesek/imhisdolly2.html