My understanding is that Michelle immigrated to the U.S. with her parents when she was young. So she could not petition her parents since they were already here. Her parents likely brought along any other siblings if they were under 21 years of age. Unless she went to the Philippines to get married to a Filippino national, she could not have petitioned any other family members. Only immediate family members can be petitioned.
I fail to see a massive "legal immigration crisis".
She can still petition for siblings over 21; it's called a "Fifth Preference" petition. Also, the "massive legal immigration crisis" is there, my friend. I've been a State Department visa officer -- in the Philippines, to boot! -- and I can tell you that we're committing a kind of national suicide thanks to our current immigration law.