the first point you bring up, she used the sharingan to copy, i'm sorry but that's bs and there's absolutely no way. Now if you wanna go with the second, extremely unlikely. The first part, she learned it faster bc she's related to sakura, now that's just the peak of this mountain of nonsense. First of all just no lol and second, in case you haven't noticed, everything rn points to sarada being related to Karin, not sakura!
Anyways for the rest of your second point, It would be ridiculous and like I said extremely unlikely if she already mastered it but even if she did, byron123 said that he used to respect kishi and not as much now bc if it is the case, as a writer he needs to at least address it to some extent first before letting sarada do that out of nowhere. For example, Kishi uses flashbacks a lot, well this will be the perfect time for him to put one panel showing sarada training with sakura on this and then go back to the present and show that she learned how to use it. Or he could even show sarada thinking smth like ok time to show what I've learned, then show her punch the ground, and then in a future chapter explain that she has been training with sakura. However, that's not the case, she literally just did it, that's why like B123 said, kishi presented it as if it was genetic which is not the case.