It means they lost their fortune. The implication is that they probably spent it quickly and in an irresponsible way. Perhaps they went on a massive spending spree and wasted all the money. The word 'blow' is used here in the sense of creating a sudden explosion. Another common collocation using 'blow' with this meaning is 'blow one's chances'. For example, if you say something incredibly stupid in a job interview, you could say that you've blown your chances of getting the job (in the sense of suddenly ruined/lost). I hope that helps.

It's an idiom. It means her parents had foolishly spent all of her money. For example, instead of saving it or investing it, they may have spent it on gambling, fancy cars, designer clothes, and lavish trips --things that don't increase in value. OTHER EXAMPLES: "He blew all his money at the racetrack," meaning he bet all of his money on horses that didn't win. "I really want this job, but I don't think I'll get it because I blew the interview," meaning he didn't do well at the interview. "He blew his top," meaning he got very angry. "He says he's going to sue me, but he's just blowing smoke," meaning he is talking tough, but he's not going to follow through with filing a lawsuit. "She gave the police information that blew the case wide open," meaning the information she provided was so dramatic and explosive that the police were able to solve the case. "I tried to talk to him about my problem, but he blew me off," meaning he didn't take me seriously and he is not going to take any action to resolve the issue. "We had a dinner date, but he blew me off," meaning he didn't show up for the date. "I saw her at the party, but she totally blew me off," meaning she ignored me. As you can see "blow" is used in many phrases and can have many meanings, but please be careful. I'm American, and in the U.S., "blow" is also used to describe a sexual act. "Blowing someone off" and "blowing someone" are two VERY different things.

A fortune here is a lot of money. To blow it is to spend it very quickly on not very much. So her parents wasted all the money she had earned in films

Her parents had spent all her money. Another expression: He blew it - he failed while attempting to do something. He thought he would pass the exam easily but he blew it.

In this context, it means "spent" or "used up". It means that her parents spent the fortune that she would have inherited. It is a very strange phrase, because it doesn't mean what it looks like.