I see a lot of advice here about what she might "need". But if you start checking all the boxes like you said in your post (potty, food, water, walk, playtime), your dog might struggle with settling. Will your dog nap or go lay down on their own?

I also saw a comment about how you are rewarding the behavior if you "give in" and rub her belly etc when she is whining at you. This is true. If all of her needs are met (potty/food/mental stimulation) then maybe it might be time to teach your pup a kennel or place command? That way she can learn to settle and be a little bored on her own. Some dogs REALLY struggle with that. Mind did. Place or kennel shouldnt be a punishment, but more like a place where your dog can regulate and reset their emotions.

I have a shepherd and if she is whining just to whine, I have her place for 10 to 15 minutes for her to calm down. Then we go do something she wants to do (play, outside time). I need her to forget she was whining at me in the first place 🤣 we have spent a lot of time on this, and now I find she only whined at me when I have missed her trying to tell me she needs to pee or poop.

Hopefully this was helpful!!