possibilities:
1) she is really stupid and was scared the guy would expose all the tapes/videos to her husband, so she complied to everything they told her to do
2) she unwilling got involved but in the end, enjoyed it (hence the 2nd, 3rd time). but it got exposed to her husband so she went to the police to get those 2 others in trouble
3) she was involved all along (I mean, who would be willing to take a shower with a friend who's NOT a best friend?) but then somehow 風聲 got exposed to her husband so she had to make up a reason and played the victim