My opinion is to use CGI to have her in Episode IX and continue as previously planned with episode IX. If they were intending to kill her in episode IX, do so. If they weren’t, don’t. Some will say it would be disrespectful and it is too. It if was not disrespectful to Cushing, why would it be to Fisher? As for being too soon, just where is that line drawn? 20 years? 15 years? 10 years? 5 years? 3 years? Where??? and who decides this? I think she would want to be in episode IX. Get the approval of the fisher’s family first of course(and don’t do it without it).
better yet why not have her daughter be put in old make up boom it would be like she was still with us. much more respectful to her family if you ask me.