Well, ya know, I'm pretty sure we live in the same neck of the woods (I'm on Vancouver Island....you're Twiggy's friend, right?) and it is HOT. It's 11:15pm and I'm sitting here at the computer in front of the fan because I'm too hot too sleep. :? So the heat could definitely be the problem....how is she during the day? Does she handle the heat okay then?
Could also be hunger, as you mentioned (growth spurt??)....not sure on the immunization query, especially a week later.
Good luck, and I hope you get some sleep.