Tantrums While Babysitting

My niece (who I will be watching for the next 8 days) is 2 and throws tantrums anytime they leave a "fun" place- friends houses, parks etc... Should I just ignore her and pick her up and put her in the car??? Advice???

Its hard when its not your child - because you aren't going to be able to make a permanent change - its more about coping.

I would suggest one simple plan. Anytime you go somewhere "fun" - before you get out of the car go over the plan and lay out your expectations. Here's a simple sample conversation:
"We are going to get out of the car and play at the park. But, when I say,'Time to Go' you need to say,'Okay'! Can you practice saying ok for me?"
"Okay!"
"Can you say it louder?"
"Okay!!"
"Wow, that was great. If you can say okay that loudly when I say, 'Time to go,' then you can have an Elmo sticker when we get back in the car."
When it is two minutes to departure, say something like...
"I am going to say, 'Time to Go' in two minutes and if you say Okay really loudly and get into the car with a happy smile then you can have your sticker!"
And then with one minute to go...
"I am going to say, 'Time to Go' in one minute and if you say Okay really loudly and get into the car with a happy smile then you can have your sticker!"
And then...
"It's Time to Go!"

I would get Elmo stickers, Princess stickers...something that they are into. You can even stretch the warnings to five minutes.

Anyhow, if it doesn't work, be prepared to scoop and go. And if there are still tears, when you get in the car remind her that she didn't get a sticker, but that if she can say Okay happily the next time, then she can have one. Don't over think it - but if you stick to your plan she will probably learn that you aren't someone who is going to give in. And you'll have a happier week in the end.

Good luck!