Nothing in Obamacare forced United Health Care to leave the California Market. It was a business decision on the part of the carrier which may or may not have happened without Obamacare. Remember, existing plans were grandfathered and didn't have to conform to the new rules. They shut this down because they were unprofitable.
Had they made this move before Obamacare, she would not have found any coverage with her pre-existing condition. The only available state plan for people with pre-existing conditions had a lifetime cap of $50,000.
There is no guarantee that United Health Care would not have made the same decision without Obamacare. Think about it. If they only had 8,000 individual customers in California and this one had already run up $1.2 million in claims, that's already $150/policy in claims. Assume they have 6 or more plans, each with its own bookkeeping and that hers wasn't the only claim on her plan, you can see that this plan was not going to make UHC any money.
Some young people will pay more, but only the ones that don't qualify for subsidies (i.e. singles making more than $45,000/yr.). What percentage of young people do you think fall into this category? If they're making that much, it shouldn't be such a hardship. Also, they won't be young forever and will benefit someday.
I sell insurance, including Obamacare plans, here in California and know what I'm talking about. The old system sucked and if anyone experiences some minor discomfort due to the changes, it's too bad. But the benefits will help millions who could actually die without them.