Ellz, talk to your mum the way you have just talked to us. That's all you need to say. I'm sure she will be glad to listen to you and advise and I'll bet any money, that she has been in the same situation herself at some point.
Why not spend more time with the friend that you do like and when the friend that you don't like asks you to meet up, just say you are busy? That way your bond with the friend you like will start getting back on track, and you will see less and less of the friend you don't like.
Please try not to get too upset by it all, be positive and stand up for yourself. If someone is not being a good friend to you, tell them.
But first and foremost, go and talk to your mum at some point today if you can.
All the best.