the marriage counsellor

i have a friend who's having marital problems. she's a good friend of mine but certain things, i'd rather not help coz i did help a 'friend' once and it backfired. from that moment onwards, i leaned a lesson not to meddle with people's problems especially marital. but this friend of mine kept calling to tell me her side of stories. trying to be a good friend, i listened but so far, i havent given any suggestions on what she should do. to tell the truth, if i were in her position , i would immediately know what to do but somehow, i juz kept quiet. i dont want to be the one who's responsible in influencing her decision. i dont think she's stable mentally at the moment. not to say that she's a loonie but she may have so many things on her mind rite now that she might not make a good and wise judgement.
here is the question...am i not being a good friend for not helping her whole-heartedly?
i would like to help but what would happen if she took my advice and things turned from bad to worse? i'm not gonna take any chances...
before we said goobye, she begged me to tell her everything if anything arises. i didnt promise anything though i value the friendship that we have. but some things are better left unsaid. i'm doing this in good faith and i think it's for the best of both parties. knowing her other half and his circle of friends, i'd rather stay away as far as possible. i was never in their good books and i juz dont want history to repeat itself.