What to do if partners friends are a bad influance?

I know it's very important in a relationship for each partner to get along with the other's friends, but what happens if you believe them to be a bad influence?

If the friends spend EVERY weekend getting completely drunk, sleeping around and just generally not acting in any decent way, having no morals, etc. What would you do?
The majority of my partners friends are like this, and while it shouldn't perhaps be a concern, she has depression and in the past she had a couple of breakdowns and they really didn't help matters, constantly encouraging her to go out drinking with them when ever and where ever possible.

Due to outside circumstances, she has lost a lot of contact with them, but I do find if she has been speaking to some of them for a day when she returns her language is terrible and she acts all 'tough'.

She has once or twice said that they are a bad influence, but I still feel uneasy when she talks to them (we live in a small town). How should I deal with this? I realise I could perhaps be being unreasonable, and it's not like I'm asking her not to talk to her friends, it just makes me a bit uncomfortable.

Tough call. People become who they associate with. However if you take a stand against them he might pick them over you.

All I can say is slow and steady wins the race.

Let me be blunt here. Sounds like your partner has a weak personality, and she will always be a "follower" and do what her friends do, just because she wants acceptance so badly. It also sounds like she has so many, or such deep problems, that she is easily drawn to self-harming behavior. This is what you have to look forward to for the rest of your relationship. Do you want more, or will you settle for this?

You are either ok with that, try to help her change (if she even wants to change), or find another gf.

In my opinion, part of what defines a person is his/her friends. So if you find yourself wishing your partner had different friends, its kind of like wishing your partner were different. If you're wishing that your partner were different, well, maybe it's time to get a different partner...

Your partner is an adult, capable of making her own decisions about her life and her friends. What you DO about it, is tell her that they make her uncomfortable, and why.

As an adult, she then decides what she wants to do about it. If she wants to do nothing about it - quite likely as she probably is comfortable where she is right now, then you get to decide whether you can tolerate it or not. If you can't, then it's time to go. You don't get to control her outcome.