Snapping and biting for attention...Ugh

Mandy has been increasingly demanding since I've been home most of the time since May. Her new thing is nibbling on me when I stop petting her. She's also been crazy with whining and gets into moods. For example, I was folding laundry on the bed and she started playing with a plastic hanger. Since she seemed playful I put my hand under the covers so she could "catch" it. Instead, Mandy took offense and put her ears down and started swatting at me! She's also been sulky and it seems like the only thing she wants is petting and being held constantly. Her appetite is fine, box habits are fine, I can't imagine what is bothering her but I wish she would cheer up!

It sounds as though your Mandy is acting like a spoiled child now that you're able to pay a lot more attention to her. Like any child she needs to have some parameters set on her behavior. A firm "No" and then ignoring unwanted behavior can often be very helpful. I've been training my cat to stay out of our walk-in pantry by standing in front of her, holding my hand out, palm facing toward her, looking into her eyes and firmly saying "No". It's working. Even cats have to know who the boss is and have to understand that there are limits to what's allowed. If you make this consistently clear to them they WILL understand and respect you all the more for it.

A water pistol can be helpful too!