The first check happens is an Anal Addict check. DO NOT FAIL IT.
If you do, due to a too high anal addict rank, it's an instant game over.
The second check is after you browse her wares. YOU WILL FAIL IT IF YOU HAVE ALL 3 EQUIPPED TOYS.
Purity has nothing to do with it, you will instantly fail the check if you have toys in all 3 slots.
That'll get you the Perfect Toy Achievement. It'll also end your playthrough.
When you first encouter her, you don't have any toy at all. If you buy 3 items, only cock cage is equipped automatically. Gag and anal plug need to manually be equipped.
For the second visit....No... I didn't instantly fail the check like you said.
Step one: I was equipped with 3 items....There was option to continue/fail(continue leads to perfect toy next step, but fail stop the perfect toy event).
But I was not an ass addict 3. So, she was disappointed that I still have my dignity. And the perfect toy event didn't trigger.
Step two : If you choose to continue on first step, you will come here. There was another pass/fail option (pass stopped the perfect toy event and fail option achieved perfect toy achievement with a game over).