For the most part, if she has an American company willing to "sponsor" her by offering a job, she can apply for a work visa. Without a job offer, she probably won't get it.
Things working against her:
1) She's young
2) If she's single, she'll likely be turned down
3) If she is poor or shows no substantial assets in her application, she'll likely be turned down
4) If she has no family of her own that she's leaving behind
Basically, the US is looking for a reason for her to
return home once she's here. If she's leaving behind something valuable, like land, a business, a husband or children, she'll be looked upon favorably. Older applicants are also favored because they aren't commonly violators of visa privileges.
It's very, very common for young women to come to the US looking for citizenship and a better life the old-fashioned way, by marrying an American man easily charmed with big eyes. (Did I say "eyes"?) This is why certain applicants are discrimminated against.
Work visas very. The ones that I've seen range from 90 days to several years. One girl now living in New York as a nanny is required to leave the country once every 6 months. She may just drive over the border to Canada for a day, but she has to have the stamp in her passport to satisfy the requirement.
Visa requirements have not really changed very much with 9-11, or so it seems. My wife's sister was granted a 90-day work visa this last summer. She's about 30, seperated from her husband and dirt-poor, but she was approved anyway. (It's common practice in the Philippines for a family go gather their assets into a pool to allow one applicant a favorable application. Those pinoys are pretty smart!)
Incidenetly, another friend of my wife's was granted a tourist's visa (10 years) and fits the same description as her sister, except that she was moderately successful in her career in the Philippines before she came and had her own assets and college degrees (post-graduate in divinity, I believe). Another missionary friend is often approved for tourist visa (single, young female) fairly often to do fund raising. I believe she's sponsored by a church in LA, and her "asset" in the Philippines is a mission she built herself from the ground up (not extremely successful, but thriving and several years old now).
I brought my wife to the country with a "fiance visa". It took about 15 months from the time we began the paperwork. This is a much more successful means of getting into the country. With only a few requirements, a clean background check conducted by the state department, and a clean bill of health by a US-approved medical facility, your friend is almost guarenteed approval. She only needs an American citizen willing to sponsor (and marry) her. The INS merely looks for evidence of a relationship, you have to meet face to face and show ongoing correspondence (that was easy for us, we wrote several times daily for two years!), you have to have photos together, you have to be married within 90 days of arriving in the states, and they delay your paperwork here in the US on purpose while monitoring your relationship after you arrive. They aren't intrusive, they simply ask for evidence that you've mingled your lives. My wife and I showed that we have joint bank accounts, we live in the same apartment, we had a baby together, etc., the normal things that married people do. (She's eligible to apply for citizenship within 5 years of getting her green card.)
If you need any more information, I'd be happy to tell more, but this post is already of publishable length!
