Isn't Weeding/Nature day on the 25th/26th of April?
On the wiki it says Phoebe's birthday is on the 22nd.
But if it was on Weeding day, I don't think it would interfere because Weeding day doesn't involve any villagers getting involved.
Oh good. I was worried since I never got a letter from her about it, I had to look it up! I am really hoping that Drago is there to celebrate with her. Because they are perfect for each other. 2 fire based mythical creatures. Plus villagers talk about the two of them being together a lot.