You cannot negotiate with a 2.5 year old. They just don't understand the concept. From your description, it sounds like you might have an underlying power issue.
Does you toddler insist on doing routine tasks such as
- Opening and closing doors
- Switching lights on and off
- Putting the nappy/diaper bag in the bin/bucket?
If not, don't bother reading any further. Otherwise, keep reading.
It can be fun to teach your two-year-old to do these things, but it can quickly become a habit and she can totally lose it if you do one of these things just once instead of her.
If this is the case, you have a tyrant on your hands so you need to stage a coup d'état. Here's how we did it. It requires that your toddler have her own room and a lockable gate so she can't freely come and go at night.
One night right before her bed time:
- Throughout the bedtime routine, restrict your talking to giving instructions and saying goodnight.
- After changing her clothes and nappy/diaper, put them in the laundry and bin and make sure she sees you doing that instead of her.
- Pack up all her toys and take them out of her room. (Allow her to keep her teddy bear, though.)
- Turn off the lights yourself instead of allowing her to do it.
- Close the gate to her room instead of allowing her to do it.
- Put her in bed and tuck her in instead of allowing her to do it.
- Keep lighting to an absolute minimum. This includes any hallway lights, for example, that she could see when standing at the gate in her doorway. (If she has a night-light, continue to use it. Children need just a bit of light so they can find their way in the dark.)
I can guarantee she will be screaming throughout the whole process as she sees her regime come crashing down. Despite step 5, expect her to get straight out of bed, stand at the gate and protest. (The point of step 5 is to establish routine, not keep her in bed.) You need to be strong and not cave in. If you cave in, you would have upset her for no reason.
In the morning, your toddler will be completely different and much more pleasant. You will need to continue showing her that she isn't in control, so don't let her switch off a light, close a door or dispose of a nappy/diaper. It seems counter-intuitive, but it makes sense once you start to understand what toddlers really need. Despite toddlers readily assuming the role of tyrant, power over their parents is a burden that stresses them out. Once you take away that burden and replace it with routine, you will have a happy and compliant toddler. And you will also be much happier.