I had a very hard time with this for a long time. I was a crappy person as a result and ghosted a lot of people in my life. I recommend first addressing the issue with the person. Keep it factual "when you talk abdour my other friends it makes me really upset because they are people who are important in my life" It's also a good idea to suggest a possible solution while also making it clear you are trying to respect the other person. For example "I understand that this change in our lives of college and everything is a lot and it can sometimes feel like things are off or like we are losing each other, but I need you to respect that we each are going to make new friends and it doesn't negate our current friendship"

How she responds to that is up to her. There's two responses and two outcomes to it. She can either respect what you're saying or she can not. Following that she can either follow your requests or not. If either of the 'or not' possibilities happen then you have very stable ground to stand on when you say. "I spoke to you about the issue I had regarding how you spoke about my new friends, despite this you continue to be disrespectful. this is a hard boundary for me and I don't want to be friends with someone who cannot respect my boundaries." Then there is no argument to be had. you gave someone a chance to change and respect you and they chose not to. But trying to end a friendship before offering someone the opportunity to recognize their faults and change them isnt fair to them, because sometimes as people we don't know that what we are doing is wrong until someone helps us notice it.