Kitten not acting right after getting shots?

I am posting from the US where I just took my kitten to the vet clinic at tractor supply for her 8week shots. I do have a regular vet that I use for her and all of my other animals but they're obviously closed since it is the weekend.

I've had her since she was 4 weeks old when her and her litter mates were abandoned in a plastic storage bin in the woods. I bottle fed her, she went to our vet every 2 weeks for deworming and shes been doing GREAT.

But today I took her into tractor supply for an 8 week vaccine clinic. They did the FIV test, and gave her two basic shots that she needed. I know that taking her into the car does not at all stress her. She always takes car ride time as nap time, so I don't think that would have worn her out so much?

But after she got her shots and I drove the hour long drive back home, she ate a little bit and went STRAIGHT to my bed where she is currently still snuggled up and sleeping on my blankets. It's been over 5 or 6 hours that shes been sleeping and she NEVER sleeps this much. Especially considering her (actual, biological, from the same litter) sister is here for the weekend and they always play non stop.

Even my senior kitty has come to check on her and licked her little head 😭🖤

Is this normal behavior? Do the shots and blood tests really make them this worn out or am I overthinking it?

The cherry ontop is that it is my birthday today and I want to go out, but as of now I've canceled all of my birthday plans so that I can be by her side because I'm worried.

(I think we have very much established a velcro relationship 😂)

TLDR; Kitten hasn't moved from my bed after getting her shots today. It's been almost 6 hours of her napping. Is this normal?