We love Math Mammoth. We’ve used it from first to fourth currently and plan to use it through level seven. It’s just set up so beautifully and love how Maria Miller wrote it. You are always moving forward, but with math your using what you already learned to move forward (kind of a built in review). There are extra worksheets, websites with games, etc if you ever feel like you need extra practice on a skill, as well as tons of free videos by her.
Here is a thread from 2014 with a more detailed response from me and others on Math Mammoth (I still agree with everything I said in it): https://simplycharlottemason.com/scmforum/topic/math-mammoth-users/
There are different series and placement tests to help you daughter with a good place to start. You could do a placement test and even send the scores to Ms. Miller and she’ll help you with finding the best place to start with the curriculum.
Hope that helps!