I think the rest of the Scooby gang should have realized that Willow had an issue with magic before Tara came along. Even in ‘Lovers Walk’ she tried to use magic to stop herself and Xander from lusting after each other.
In the earlier seasons, I hated Cordelia and always wanted Xander and Willow to get together. Everything changed for me in Lovers Walk. When Xander broke Cordy’s heart, I felt so bad for her and cried.