You need to make sure she's prepared for the experience of going through Immigration and Customs in SFO. She needs to know what kind of questions they are likely to ask, and to prepare some answers in advance - in particular answers conveying the idea that she is coming for a short visit and will be returning to China on a specific date. She should have all the necessary documentation ready, including eticket receipt (showing her return journey), your parents' address and phone numbers, and your SFO friend's address and phone number. Does she have enough English to answer the agents' questions, or is she going to need an interpreter?

Although not without its own risks, you might want to encourage her to attach herself to someone she meets on the plane who speaks enough English and Chinese, and is familiar with clearing Immigration/Customs in the US, so that she can stand in line with that person. While she'll have to go to the desk on her own, ideally she could go first, so that if there are any problems, the person she has "befriended" may be able to step in and help.

Likewise, you could give her a bilingual note to use at EWR that says something to the effect of "Could you please help me because I don't speak much English. I need to find the connection to Gate A_. Could you please show me the right direction. Thank you."

You and your SFO friend, and you and your parents, should prepare contingency plans if she doesn't show up within a certain period of time after she's expected. Send them a photograph of her as well as her full name and passport details so they can track her down if she disappears into the bowels of the immigration system (or simply gets lost at the airport).

Ideally, she should be equipped with a portable phone or blackberry that will work in North America. Having your friend give her a phone once she gets to SFO may be too late, since she might need it reach him/her.

At SFO and CLT, your friend and parents need to scope out a clearly labelled, uniquely identified place to meet her.