She'll soon discover which buttons to push to get the response that she desires. And you can be sure she'll push them again and again. Otherwise, you set yourself up for failure. Do increase your expectations as your child grows. Once you make a rule, enforce it.
Inconsistencies confuse a learning child.
Try to follow through on your rules in a predictable fashion. If you say that it will be time to leave the playground after your child goes down the slide two more times, then do so. Of course, it's impossible to be 100 percent consistent in all things, all the time. There's room for exceptions. Explain why a deviation from the norm is special and just for that day.