Flex can make SSL call by simply specify "https" in the url of HTTPService. However, the enclosing page must be in https for this to work. Otherwise, you may get "Security Sandbox Violation" like the one below:
*** Security Sandbox Violation ***
Connection to https://graph.facebook.com/me/friends?access_token=xyz halted - not permitted from http://localhost:8888/xyz/xyz.swf
