Ridiculously noisy neighbours

My 82 year old mum has lived in her apartment block for 21 years. A young family (couple with baby) are renting the apartment above hers.

Up to 3 times a week they have upwards of 20 people (including lots of young children) in their 2 bedroom apartment. The adults are out on the balcony until all hours laughing and carrying on, while the children are running around and screaming on the floor above my mother. They continue until well after midnight.

They have been spoken to many times, the strata manager has written to them several times, but they pay no attention.

Today, when my mother arrived home after being out, these people along with 50 of their friends (and about half as many kids), had set up a BBQ in the underground car park & had the security door to the apartments propped open so that they could come & go between their apartment & the carpark BBQ without being hampered by having to open a door. The kids were running wild all over the complex.

When confronted and told they were not entitled to take over the common areas, they claim they are doing nothing wrong.

It is getting to the point were my mum's sleep is continually being disrupted as is any chance of any peace and quiet on the weekends.

Nobody seems to be able to do anything to get these people to understand how inconsiderate they are being.

It has gotten to the point were my mum thinks she needs to move.

I am so angry, as I can't understand why a quiet 82 year old women needs to be forced out of her home.

Would appreciate any help anyone can offer with what we can do to put and end to this nightmare.