Like others have said, you have not ruined her. As a reading teacher, I can tell you that if she is at a Rigby reading level 16 in mid-1st grade she is just fine! Up until our district adopted the Common Core Standards and a new reading assessment program, we expected 1st grade students to be at a Rigby level 16 at the END of 1st grade. And Kindergarteners were expected to end the year at a level 6. Now we expect a little higher at the end of 1st grade. As a reading specialist, I would agree that redoing kindergarten would not have benefitted your daughter. If she was already reading, the beginning of kindergarten when kids are still learning the letters, would have been terribly boring for her.
Don't expect perfection from her. I was just doing some math with my 1st grade student. It was hard for me, but I didn't point out the 2 and the 6 that she had written backwards. I only pointed out the 18 that she had written as 81. It is hard to make that mind shift, but if you focus on the strengths first and don't focus on perfection, kids respond better. They are less likely to give up.
In our reading program we coach parents not to correct or point out every error that the student is making. If it doesn't affect meaning, I don't correct. If a my daughter reads "feet" instead of "paws" so what. They basically mean the same thing. In working with 2nd graders, then I expect words to be read correcly. But even then if they read "a" for "the", no big deal. If it doesn't affect the meaning of the text, it probably doesn't need to be corrected.
When I listen to students read I give them what I call 2 hugs and a push. Two things that they did great! Not empty praise, but specifics. "You did a great job using the picture to help you with that word." "You did a great job looking at the first letter of that word to help you read it." "Wow, when you read that part it sounded just like I imagined the character would have said it!"
The push that I give them is ONE thing from the whole book that was incorrect. Even if there were 10 errors. And I always give the reader a chance to reread the sentence before I tell her what was incorrect. If she reads it correctly I praise her for fixing the mistake that she made earlier. If she still struggles with it I help her figure it out.
When I read to kids, I purposly make mistakes. Then I model how I fix those mistakes. I make the comment, "Oh, that didn't sound right!" or "Oh, that didn't make sense!" Then I go back and reread it. I don't say anything derogatory about my error. Not even something as benign as "Silly me!" When I'm fixing my mistake I talk aloud about what I can do--look at the picture, use the first sound, look for a chunk of the word that I know, think about what would make sense. I do the same thing with my own kids at home. When I make a mistake, I try really hard not to make a big deal out of it and show my kids that I can fix the mistake.
At the conference, I would ask the teacher what the expectation is for work that comes home. I know that most of the things that my 1st grade daughter brings home are not anywhere near perfect. They aren't graded, and she isn't expected to redo or correct them. I have her tell me about the assignment and ask a couple of questions about it, but I don't point out her errors or make her correct them. With the move to Common Core Standards, teachers are doing a lot less with worksheets and homework. Students are doing more authentic pieces of work in the classroom. To be honest, in the 1st grade classrooms in the school where I teach, about the only paper work that I see are assessments, math pages, some word study (spelling) sorts, and writing assignments/journals.
I am working with several 1st grade students who are struggling with reading. None of them are reading at as high a level as your daughter. It is true that parents know their children better than anyone else. BUT, you also need to trust the expertise of your child's teacher. From what you have written it is hard to know exactly what your child is "struggling" with. It is entirely possible that they are things that are just being introduced and she isn't expected to know them 100% yet. A big part of the Common Core is that a skill is taught in 1st grade and students are just expected to get a general understanding of the skill. In 2nd grade, students cover the same skill and go a little deeper with it. In 3rd grade, that same skill is expanded on. I am always telling my husband that he needs to back off a little when he helps our daughter with her homework. He looks at it from the perspective "this is what she needs to be able to do eventually" instead of the perspective "this is what she needs to know now."
Trust me, if your daughter is struggling that much, her teacher will let you know at conferences, if not sooner, that there is a concern. Contrary to what some people believe, teachers do not want to see students fail and they will do whatever they can to help. They are also more than willing to let you know what you can do to help. Sometimes that means backing off a little bit.