I understand this feels complicated but it really isn’t. She is married. You need to terminate the friendship and tell her clearly that based on the feelings already shared, it is morally wrong to have this emotional relationship with her and also distressing to you to see her being mistreated. Let her know there can be no further contact and she needs to focus on her marriage.
What happens down the line must be that she decides to stay in her marriage, or not, based only on what that marriage is about. If she finds she must leave him, that must be a decision based exclusively on that marriage.
Will she leave him and show up at your door? Who knows. Don’t wait for her. It would be torture. See nobody, or date other people. If she comes to you free to date, you can revisit the situation based on your life at that time.
Among other issues, your relationship would never be right if you enter it wrong.