She also says she buys stamps off ebay. Shown below, this was the first picture of hers I noticed on the group.
She didn't listen.
Further investigation into her posts in the group reveal another visibly, but faintly, postmarked stamp across the bottom part of the neck by the 1st indicator..
I can perhaps forgive a one-off mistake, but this is ongoing.
The black scrub-out is mine as I don't want to show the names of the unfortunate recipients who may have to pay the surcharge for the sender's criminal behaviour.
Royal Mail's postal fraud online form isn't particularly helpful in this instance.
On the incoming front, yesterday, I received a letter from the US - the stamp had sticky tape on. You might just be able to see the different colour paper underneath the stamp on top of the envelope.