Was I rude?

Two of my closest friends and I have begun going for morning walks in a ground nearby. My sister has been having a bit of a tough time, and she doesn't have too many friends to socialise with. Mum and dad want her to get out of the house too... they suggested she joins us. I told her she could come with me, but it would be better if she walked at another part of the field. I said that because, she is very different from my friends... and the whole group will get awkward. My friends will feel awkward... and it won't be fun for anyone involved.