admission to IS grade 10

My friend studied in a Chinese school till secondary 2.She holds American Passport and is transferred to a public school in the US last year for Grade 9.
However her family is moving to HK and wants to put her in international school in HK for Grade 10.

Her english is average (C) in US. She can handle classes and communication in English, and do very well in all other subjects in US(got mostly A for all other courses). She speaks mandarin. She wanna get in university in the US so we hope to go for the American system more.
I personally study local school and have little knowledge in IS, so I have a few questions and hope you guys could help answering, please~~~~


1). Which of the following schools should she apply (That she has a higher chance to get in?)

- AIS (American International School)
- CAIS