Check out Aldiko, which supports the BN DRM scheme - any epub reader can read Nook format books but it has to be able to open the files.
BN uses a hash of name and credit card number to restrict access; Aldiko is able to open BN titles once it's set up.
... I got my daughter a NABI forChristmas and was hoping she could read her books on it. At this time her tablet doesn't support google play so I am out of luck with the nook app. ...
Note that 1mobile is a 3rd party app store with around 200,000 apps, and if the NABI allows installing apk's for 3rd party apps, it should be possible to install the 1mobile store. I've got the 1mobile store and the GetJar store on my 4.3" Android player which doesn't have googleplay, and searching on the 1mobile site shows that they have the Nook app version 188.8.131.52.