Research on abuse and helping a friend

[Renweard]

Hi this is my first post so here goes.
I have a dear friend who was sexually abused by her father at around age 13. Now she's 18 and is in a long term relationship with a guy who emotionally, and sometimes physically, abuses her. He controls nearly every aspect of her life and has a mean streak. He dumped her for a short period and she was very happy and things were going good but around 4 weeks ago he charmed her back (her words) . She's afraid of him, but she insist she has feelings for him. She is reaching out for help though. So my question is this: What/where is a good place to do some research on sexual abuse and it's effects, so I can at least get some grasp of what she is/has gone through? And how can I best , if at all, help her? Any sites or books to check out would be appreciated too. Thanks in advance.