She came to play with me or whatever and there was an item on the page so I bought it, and then I refreshed and Subeta was down. I had no idea what I was doing because I've never encountered her before... just for future reference, what do I have to do?

You don't have to do anything. She gives you a big bear hug and an item. :) The item you saw was what she was giving you.

When she asks you to play with her, you just click the text in the random event and it'll take you to a page, she gives you an item as thanks for playing with her (as well as a virtual bear hug) you didn't have to buy anything. :D

Oh, okay! I was thinking it was a quest type thing like for the bumbus! Thanks so much!