I can't imagine an ethical breeder even wanting you to have a pup you didn't want to have. The size wouldn't bother me too much probably because I love 6 lbs but if this yorkie doesn't look like the same one, then that is different.
I would call her or better email her so you have something in writing and tell her, the minute you saw her you knew it wasn't her but didn't know what to do. Tell her you were so counting on the other and you're very upset about this and would take $1000 back even though you pd. $1200 a few days ago. Tell her you belong to a yorkie site with 24,000 members and would like to be able to brag about how nice you are rather than the opposite. What do you think?? Easy for me to give your $200 away
but heck if it gets you out of this.