I have a Nexus 7 and playbooks. The Nexus 7 is smoother, faster to respond and has far more apps available. The playbook is far more solidly built.
My kids (4 & 5) have a playbook each and they pretty much use theirs for educational / drawing apps, angry birds, playing music (chipmunks....arrgghhhhh...why did I put that on there!) and watching films - all things the playbook handles very well. It is very good for video playback and has mini hdmi out for connecting to the TV.
As your daughter is a lot older than my kids is there a chance she might be limited by what's available on the app store. Mine do keep asking about Shark Dash and Where's my water, lol!
No playback from a usb stick, but easy to transfer data via PC as long as blackberry device manager is installed.
There are a few android apps that have been converted, but they're honestly few and far between in the grand scheme of things, and apps properly coded for the playbook run better.
I have read there are more apps in the wings after the new OS update that's rumoured to be due within a few weeks. I would say that £130 is a great price for the 64Gb tablet, depending on its usage. If I had to choose for myself I'd keep the Nexus 7. If I chose for my wife or kids I'd keep the 64GB playbook as they use the browser and video playback more, and don't need (but might like) the other apps available under android.