Lamium album, commonly called white nettle or white dead-nettle, is a flowering plant in the family Lamiaceae, native throughout Europe and Asia, growing in a variety of habitats from open grassland to woodland, generally on moist, fertile soils.
L. album was introduced to North America, where it is widely naturalized. The young leaves are edible, and can be used in salads or cooked as a vegetable.
Bees, especially bumble bees are attracted to the flowers which are a good source of early nectar and pollen, hence the plant is sometimes called the bee nettle (source)
So can guinea pigs eat dead nettle?
Unfortunately they can’t at all. It is not good for them to eat and should be avoided as a food for them.