Can we focus on that scene?
‘Coz, guys...
Alya knows.
She saw how Nino tried to convince Nora to let her sister go on fireworks show. She saw how he was upset since the only reason he won is because Marinette cheated and helped him. She saw how he tried to rescue her, fight with Anansi and help Ladybug and Chat Noir.
She was aware that her boyfriend was insecure and kind of humiliated that day and, moreover, has no self-esteem in general, so she did whatever she could to cheer him up: she completely ignored Ladybug - her idol - and made him more important on her blog.
The most supportive girlfriend in this show.
Also, can we appreciate that Alya recognized Nino in a second by one word, but Marinette and Chat Noir after almost a year still have no idea that their crushes are also their best friends?