If you genuinely want to see your mum without your sister, have you tried expressing this to your mum? If you were to say something like, "Mum, I'd really love to spend a little time with you as I miss seeing you on my own (or just as my family). It feels different when I come over and my sister is there. I don't feel like I (or myself and the kids) can connect with you in the same way as we do on our own and I would really appreciate some special time just for us. Is this something you would like to do too? Can we plan a time in the next week where it's just us? "
You may find that you get some alone time with her. Acting as a confidant means you aren't expressing your feelings, you're just listening or trying to problem solve.
I think expressing your feelings and understanding what your wants and needs are (not your mums) and trying to get them fulfilled is going to put you in a better place than trying to take on your mums problems for her.
In all likelihood if you phrase a question like the one above, the chances are she will want to try to free up some time to see just you (or your family) and that in turn may start the process of her seeing it's okay to be busy or unavailable if your sister comes calling. So it may end up being a bit of a win win.
Good Morning Monday 29th April 2024