H.W.
Hi Galway Girl,
My son did this too. He goes through 'seasons' (we're in one right now, The Season of Little Resilience and Much Negativity... I am mourning the loss of the previous Season of Sunny Disposition and Enthusiasm.)
Besides sticking with our usual boundaries/rules, here are some things which helps me a lot when my son flips that internal switch:
Being consistent.
Being empathetic; this often involves stating the obvious ("I know, you really wanted to have ice cream today and it's not a treat day and that's a bummer for you.")
Giving a firm NO when necessary and, whenever possible, a "YES and WHEN" ("Yes, you may have some ice cream tomorrow. That's your treat day!")
Giving lots of positive attention during times of 'neutral' behavior; that is, when he's busy doing something he enjoys for his own pleasure, that's when I rub his shoulder or back, tousle his hair, give him a kiss on the head or a wink or smile across the room. This non-verbal contact is very validating and has a profound effect during times when we see negative attention-getting behaviors such as you describe.
I also often Google "child development 5 years" ; a website for caregivers called All The Daze is great for this and has suggested activities:
http://www.allthedaze.com/sdevelopment.html
Some whining warrants "please go take a break in your room until you can come back with your regular voice" , so once the problem has been identified, he's received empathy, offered some options or comfort, if the carrying on continues, then he's welcome to take his bad mood to his room.
Lying: I focus a lot on how HAPPY I am when he tells me the truth. When he seems a bit cagey when I ask "so what's going on here?" and then tells me the truth, I tell him HOW GLAD I am to know what happened and then we focus on fixing it. There is a moderate loss of privileges for lies. Here's an article which really helped:
http://nymag.com/news/features/43893/
Know, too, that maybe her emotions are feeling huge for your daughter and that when she's in her room for a long time, she's taking a break. I've seen kids do this in my experience as a nanny; one in particular would keep coming out so stinkin' mad that her mom would have to carry her back in. So your daughter is doing some self-regulating by staying alone.
If this continues on for months, do talk to someone, but otherwise, my guess is that it IS a season, and just as that little girl I cared for grew out of it, yours will also.
Good luck.
Oh, and I should add, I wouldn't mention Kindergarten or big transitions until you are close to them. Talk of KG can add a lot of anxiety for kiddos-- I've seen this many times as a nanny and preschool teacher. Try to keep her in the present as much as possible, otherwise it's a big unknown and added stress.