Since nobody else has explained why so far, the smoking gun that makes it clear it's not a dot matrix printer is that dot matrix printers put ink onto paper usi

Since nobody else has explained why so far, the smoking gun that makes it clear it's not a dot matrix printer is that dot matrix printers put ink onto paper using pins to strike a ribbon. They work on the same principle as typewriters did, which also used a ribbon. (https://en.wikipedia.org/wiki/Typewriter_ribbon https://en.wikipedia.org/wiki/Typewriter_ribbon) The reason they're called "dot matrix" was to distinguish them from another contemporary type of printer that had type (letterforms) built directly into a ball or wheel, so that instead of an array of pins, a raised metal piece in the shape of (say) an "A" would strike the ribbon. ("Daisy wheel" printers were of this type.) These had nicer-looking, non-pixellated type, but they were slow and couldn't do any graphics. So if this really were a dot-matrix printer, she would have been putting highlighter ink onto a ribbon, but she was putting ink into a reservoir.