I think the way it probably happened was, a casual conversation with Haz about her trip to Disney. Haz going ott about how she's always wanted to go, dream holiday etc etc. Basically hinting big time about being invited along. Then Ana saying 'ah you should've booked too'
Then Haz literally rushing off to buy flights and tickets.
We've all seen how passive Ana can be. She's very easily manipulated and peer pressured.
She definitely wouldn't have to bollocks to tell Haz she can't come.
Maybe I'm wrong and Ana just asked her. But given their personalities, I'd say Haz invited herself and Ana went along with it.
She will also just be going along with whatever Haz wants to do there. She's pretty weak mentally and definitely not as confident with friends as she'd like to think.