Thanks to someone mentioning it in Niomi's thread, I found it! (Eventually...)It wasn't a posed for ad (would've loved to see that though ), but she put a picture/story online of a box full of toilet paper from some brand/store (forgot which one). It was obviously something they got for free.
It was mentioned in her threads, I'll see if I can find it!
Zoella doesn't even have to pay for ger toilet paper
Edit: thanks @lilamay !