My girlfriend's friends

I think my girlfriend's friends are a bad influence to her that might lead to her cheating on me or being endangered. What can I do to encourage her to get better friends or encourage them to me safer.

This isn't really your battle to fight. Your gf will either act appropriately or she won't. Her character is hers to own. You have a decision to make. Do you leave her because you are worried she will cheat? Do you stay with her and watch her to see if she cheats? Or do you stay with her and choose to trust her? All have their perks and drawbacks. If you leave her, you no longer have to worry about cheating but you have lost someone that (I assume) you care for. If you stay, but watch for cheating then you get to stay with someone you care about but you'll be living with that constant stress. If you stay and trust her, you have the highest likelihood of potential happiness but if you are right about cheating being a concern, you also have the highest risk for heartbreak.....and std's.

It your business who you are with but if your GF shares your values and standards that determine whether it's worth your time and effort, then you wouldn't need to worry about her choice of friends or their influence over her which could lead her to go elsewhere. Step back and have a look at her properly because if you doubt her loyalty now, for whatever the reason, you will be in doubt for whatever time you stay with her. You either accept her 100% or you don't. It not your responsibility to encourage her to hang out with better friends, rather it's your responsibility to look out for yourself and be with a GF who has a need to keep your heart safe.

Their should be 100% trust in any relationship. If you haven't got that then their isn't much hope..if it is however an emotion of panic from you that she will then I would seek advice about that. If she loves you enough she shouldn't do it at all. It's give and take in any relationship. If her friends are a bad influence on her I would talk to her and say that you aren't keen on how her friends portray them self's and you don't want her to be like that. Sometimes we have to just speak our minds. And not be scared of what people might say. Obviously in a reasonable manner not disrespectfully. Best wishes and good luck to you.