My four year old's behaviour

[Megansmum1985]

Please help,
My daughter is normally a beautifully behaved,well mannered,articulate and sensible child.She is an only child but very sociable and has great social skills.When she is with my niece who is six, she is a nightmare.My niece can be mischievous and rather bossy and I think my daughter tries to impress her by suggesting awful things like putting the garden hose through the cat flap and turning it on to flood the house,then filling putting soils and leaves through the cat flap.When trying to discipline them they just laugh and run away and begin again.It's like a pack mentality.What can I do to stop this and why have they got this pack mentality when they are together?
Thanks

You need to be a lot sterner when telling them off by the sound of it. They flooded the house and then ran off laughing and did it again when you tried to tell them off?!

You need to speak to them in a stern tone, possibly with a slightly raised voice in order to make them realise you are serious. They need to be given cloths/dust pan and brush and made to clean up the mess they made. Then they need to come in from the garden and play something nicely inside.

If/when it starts to get destructive again you need to separate them. DD can go to her room and niece can sit in the kitchen/living room until her parents come.

She also wouldn't be getting invited back again if this is a regular thing!

Most 4 year olds are very susceptible to the influences of an older child, but that doesn't mean they should get a pass for their behaviour. Allowing her to run off laughing after behaving so poorly isn't teaching her anything. She very quickly needs to be shown the consequences of her behaviour.