Leaving someone out and dreading their reaction

[time4me]

How do you stop dreading the reaction of an overbearing relative or friend when they feel they have been left out? I personally do not have a problem if I am left out of a weekend away as I believe in personal choice and also there could be a reason.(not that I would ask or query it)
However I dread the reaction of the ones ( or one ) I dont invite to the point where I feel it is just not worth even asking in the first place.To illustrate,I went away to a caravan with my mum for the weekend,one sister txt me "So when are we going away?".She obviously felt jealous and resentful of the fact that I had asked her over my mum.I have 4 sisters and so it isnt always possible to ask all of them away at the same time,but if I ask one over this one sister (or my mum who is equally resentful if she is left out of anything)I dread the reaction,and it has even cancelled out any sense of relaxation at going away,such is my sense of foreboding.
Any wise words,sympathetic words,books to read or one-liners would be appreciated.
I know I struggle with assertion and I am extremely sensitive (long story),but I do feel resentful.This one sister in particular is very supportive in many ways but I feel irked by her attitude.This is someone (the sister) who has issueswith having a controlling mother!I do to which I think has made me very sensitive about not repeating the pattern .Thank you in anticipation.

You are reading too much into your sister's text. "She obviously felt ....". Not obvious at all. Deliberately take it as a lighthearted, jokey comment, regardless of what you fear she may have really meant. Reply something like "this year next year some time never" (although that's rather a long text) or better still just ignore the issue and text back "mum & I enjoying selves".

I wish I had a sister! I'm always telling my dds how lucky they are to have each other.

Elastic,you have made me feel better.She is a good sister is lots of ways,thank you x

Perhaps she touched a nerve of guilt, or you anticipated a reaction from her and then read that reaction in to what she said (even though it was quite an innocuous text, and I don't think she necessarily meant it like you thought. Agree with EW.)
Why not text her back and say 'yeah, that would be great'?

Thanks,I did have a chat to her and she said she only meant she was eager to go away with me and not that she was trying to monopolise me.Thanks for the advice,I still feel uneasy but I must say your comments made me much better.Thank you.