Ms. Kitty, who is normally a playful and curious cat, hasn't been playing or active at all. She's eating and drinking water, she is also using the kitty box regularly. She chewed on that plastic packet that catches the blood in a package of meat. I found the remnants next to the trash can. Sense then she's just been laying around, or sleeping. None of her other habits have changed.
It sounds like something in the blood on the package or the package itself disagreed with your cat's system. Her immune system probably kicked into action and is making her feel less lively. However, although this can happen for a few days, if it continues without seeing any improvement, then I suggest you get her to the vet in case she ingested something that is more harmful.