Thank you for the question. Here is information on mulberry plants and their berries: https://www.extension.purdue.edu/extmedia/fnr/fnr_237.pdf
As Master Gardeners and due to the limitations of this electronic format, we can't tell you if your girlfriend is eating berries safe for human consumption. The best bet is to get accurate identification from someone who can see the plant these came from. Common sense tells us that food from the wild should never be consumed before accurate identification.
Thank you for contacting Extension.