Open Question: Is it really better not to accept a 3 months contract for work?

My cousin found another job and went for it, she signed the 3 months initial trial contract and she was doing well and everything was fine but in the middle of the trial she noticed how her job was getting less and less busy.... as a result she was dismissed due to the low demand in the business.... So now she has no job and is not so easy to find a good one out there.... This is terrible!! Well what to do but just go through this... Anyway the question is... is it really worthy not to accept a 3 months contract and rather find a job with a permanent contract straight away? Because in this situation she quit a job for good but now she is unemployed! If she didn't accept this trial then the company probably wouldn't have taken her in But the thing is that heaps and most of companies do this trial period and we don't want to be without a job you see.. how to know, what is the best thing to do then when looking for another job?? How to do it safely?