I would love to see a photo that shows Ruby driving Euins away on a police motorcycle….
Although she doesn't specify Euins or a police motorcycle, she must surely be talking about Harkness and Euins on his three-wheeler, but Harkness is in uniform and looks absolutely nothing like Ruby.
As far as I'm aware, the only time Euins is on the back of the three-wheeler is when he is being taken from the railroad area to the front steps of the Depository building, so Adams would have seen him arriving rather than being taken away.
Unless she's talking about a completely unrelated incident it doesn't make sense.