New "friend" is a bit of a snake?

[nananananannanananana]

We are a group of 8 friends who met through work.
One girl we will call her "Lucy" was introduced to us through one friend and started coming on weekends away and nights out etc.
She seemed nice enough but I'm always wary at first.
Then about 6 months ago Lucy brought her friend "kelly" out and she started coming on nights out etc.
Now I noticed straight away Lucy would slag Kelly off to us,say she's a bit simple blah blah
Try and make her look stupid any chance she got.
Then a month ago Lucy told us she had stopped speaking to Kelly and it was pretty obvious she had been bullying her.
I've got bad vibes about her
How am I meant to associate with her when she's irritating me like this ?

Anyone ?

Stop going out with her

Would you mention it to the other girls ?

Yea I would mention it to the other girls especially if you’ve all known each other longer, how awful for Kelly to be picked on like that. Has anyone ever pulled Lucy up when she is bad mouthing someone?

I'd have asked her at the time why she was being so mean/rude to Kelly. To mention it after the event could potentially look as though you're finding reasons to 'bitch about' her to other friends, but then again, if she's like this in general, people will have noticed.
Would be a real problem for me to remain friends with someone who did this.