Not quite a scammer, since she doesn't have a "clever" plan for her requests, but here's one for you anyway.
Where I work we have this one old lady who comes in every day and just parks herself at the counter right next to someone who's ordering. Doesn't matter that there's a line.
She'll also always try to get something for free.
The other day while she's waiting in line (!!!) I go ahead and make her sundae and sit it next to the cashier, indicating whose it was.
This old bird asks, TWICE, "Are you giving this to me?"
Both times I say, "No, but this person will be happy to ring you up for it."