After dabbling in far too many math curricula as supplements to my main curriculum (Singapore)—Miquon, Beast Academy, Math Mammoth, Life of Fred, Math Facts that Stick, Rod & Staff, and some even more short lived one I cannot recall—I have finally one to the stunning realization that 1) there is no perfect curriculum that does all the things (fun/enjoyable/engaging, hits math facts, deep on concepts) for all the students and 2) the best one is one I will stick with consistently.
That being said, I see that you are concerned about mastery, basic math facts, a program that does not feel scattershot, one that is gentle and likely to help your daughter build confidence, and is teachable by a non math teacher.
While Singapore is my main program, I would suggest considering Rod & Staff—a far less “cool” but totally solid program. Easy to teach, gives pretty scripted lessons for instructor, inexpensive, and math facts will absolutely be mastered. It is mastery, but there is constant review. I mean, constant review, but as the instructor you can incorporate as much or as little of that as you need. Everything moves forward in a logical progression and each step is totally drilled down before moving on. Things start slow, but in about 4th grade they pick up and you’re covering most of the same topics you would with a faster moving curriculum (I cross referenced R&S 4 to Singapore 4, and R&S5 to Singapore 5, they hit most of the same topics but often in a different order). I also like how they introduce concepts very concretely (skip counting with coins, fractions by using a ruler).
Last year we had a math hiccup with my eldest (then 4th) where he had forgotten some things and was feeling discouraged in Singapore (he was a year ahead, so I think doing 5A). He hated math and thought he was terrible at it. So we took a break and did the last half of R&S 4. It felt easy for him, and after a month or two we returned to Singapore and he was a new child. Confident, flying through the rest of Sing5 with ease. So now I have all my kids do R&S as independent work and Singapore with me, so the extra review and drill actually happens (I had been slacking on that, and Singapore expects it).