The Sister Who Stayed
When women talk about going no contact with their mother, they usually describe it as one relationship ending. What most of them find out over the following year is that it was never only one. The sister who used to text every day gets vague. The brother who agreed with you at the time now says he doesn't want to be in the middle of anything. Nobody announces a decision. You just notice, eventually, that you're on one side of something and they're on the other. There's a pattern underneath it, and it's less personal than it feels.
Consider the thing nobody says at family gatherings. Siblings who both have a decent relationship with their mother usually have a decent relationship with each other, and it isn't because of loyalty or shared history. Contact runs through her. She's the one who mentions you had a rough week, who passes along the news, who picks the date everyone shows up for. Remove her from the middle and the two of you are left building a relationship out of nothing but your own interest in each other, which can turn out to be thinner than either of you assumed.
So part of what happens when your sister goes distant is mechanical. The thing generating your closeness was the mother relationship, and you stopped participating in it. She didn't have to reject you for the contact to drop. She only had to not replace what your mother used to do.
The part that does more damage isn't the leaving. It's the distance between two siblings' relationships with the same parent. It isn't the daughter who left who strains the sibling bond, and it isn't the one who stayed. It's the gap between them.
Consider what that gap asks of the sister who stayed. Every time she sees your mother, she hears an account of you that she can either dispute or let stand. Every time she talks to you, she's holding information she isn't sure she's supposed to have. She gets asked to pass messages. She gets asked for updates about where you're living and whether you're speaking to anyone. She gets asked to agree, sometimes outright, more often by the way a story about you gets told in front of her and left sitting there.
None of that is comfortable, and the cheapest way out is to reduce contact with whoever is generating the most pressure. Usually you, because you're the one who changed something. Your mother's behavior is old news to her. Yours is the new development.
Ask siblings who ended up aligned with the parent how they chose, and most of them will tell you they didn't. They were assumed onto a side because they'd always been closer to that parent. They were asked so many times that agreeing became less work than resisting. They were told, in one way or another, that the relationship would cost them something if they didn't. Some were pushed onto a side deliberately, by a parent who wanted them separated from the person who left. You experienced that as your sister taking a position. She experienced it as being handed one. Both of you are describing the same event, which is why the conversation about it goes badly every time you try to have it.
There's no point pretending it always works out to a misunderstanding. Some siblings deliver an ultimatum and mean it: contact with me is available again when contact with her resumes. Some knew what happened to you and decided their access to childcare, money, or holiday invitations was the more pressing concern. Some watched you disclose something serious and told you that you were lying or exaggerating.
And some sibling relationships were never much to begin with. Plenty of women discover they've been mourning a closeness they'd inferred from proximity. You lived in the same house, you had the same last name, and you assumed it added up to something. It didn't, and the estrangement didn't destroy it. The estrangement just took away the occasions that had been covering for it.
Underneath a lot of these splits is a division of labor that started early. One child got treated as the one with an opinion. Another got treated as the one who helps. Daughters in particular get raised into the useful role and then measured by how well they do it, while a brother's job is to have a life. By the time everyone's in their forties, the sister who was assigned the helping job is often the one who left, and the sibling who was never asked to do it can't understand what she's so angry about. He's not lying when he says the family was fine. His was.
So what do you do with any of it. Stop using her as a route to information. Every time you ask what your mother said, you make her the messenger again, and the messenger job is the one most likely to make her withdraw from both of you. Say out loud that you're not asking her to pick. Siblings who stay connected across an estrangement almost always do it by negotiating two separate relationships that don't reference each other. It's an awkward arrangement and it works better than the alternative.
Expect it to hurt anyway. Having a separate relationship with your sister isn't the same as having her understanding, and a lot of women find the ongoing contact is its own particular ache, because she's right there and still doesn't see it.
Then decide what you can live with. Some of these relationships come back once your mother is no longer the switchboard, usually years later and usually smaller than before. Some fade out with no argument and no ending, which is its own strange kind of loss because there's nothing to point to. You don't get to control which one you got. You do get to stop waiting on a verdict from someone who was never in a position to deliver one.