"Tea party" is NOT equal to "Tea bag".
A tea party is an event.
A tea bag is an object.
Not only that, many tea drinkers don't even use bags; not all tea parties have them.
I speak from a lifetime of tea party experience. We had tea regularly when I was a child, we had tea parties as well. I also had tea parties with all my children on a regular basis. When we were broke and didn't have lots of food lying around the house (which is actually a more healthy way to be) afternoon snack time is generally a tea party at my house. We sit down, we have a pot of tea with cream and sugar, and I fix whatever we have. Cinnamon toast, maybe cookies or cake, if we have tinned oysters, we have those, cheese. You get the idea.
It's a tea party.
A tea bag is just a little bag of tea. Big difference.