Bitcoin is a great for side income, this can be a temporary solution to your sister financial situation, but they should looking for a permanent job, we don't know how long Bitcoin can survive and Bitcoin price keep on changing, and the good news is after you got the job you still can earn with Bitcoin as your side income
Bitcoin is a way to get some extra income if you have a serious business, but if you don't have one you may treat bitcoin like a real business because one day it would cover all your bills. A lot of bitcoiners here are starting by promoting signature ad campaign and then later move on to the most profitable side of bitcoin which is buying and selling bitcoin. There are guys that also buy and save bitcoins in form of business and wait for the price to get higher in future and then sell their bitcoins with huge profits, they are called "bitcoin holders".
There are as well other possibilities to earn bitcoins if you have skills.
Be a designer, open your own casino, write a blog and earn from the ads.
It does not have to be only trading or the campaign, the world is full of options, you just have to find them.
And for the time untill that happens, there still is campaign.