It's bizarre that your sister and the love of her life have not taken it upon themselves to research their options for immigration. That sort of thing should not be your responsibility. I don't mean to be harsh, just truthful.
They are very young. What's the rush? I agree that her boyfriend should look at gaining some qualifications or a degree before he makes the leap. He would have a lot more options this way. Quite a few people awaiting PR do have to rely on their significant other for support, but this is their significant other, not their partner's parents! I personally think these two should revaluate things and see if they can wait a little while. Two years is a long time, sure, but they're so young, and immigration is a huge step to take. It's not easy and it can put a strain on any relationship. (I'm sure you're aware of that, but they may not be.)
I think you should be real with your sister. She needs to realize it's not all rainbows and butterflies and that this is real life. There's not always a quick option or an easier way to get around the rules. They might have to wait a bit longer, but if they are really meant to be together forever, what are a couple more years of waiting?