Yeah, Dreamworks has made it pretty clear and put a lot of emphasis on the fact that this is Rihanna's album. Jen might get a feature but I highly doubt it; like you said, her role is too minor and a collaboration between a major and minor character would be weird. This album has been in production long enough that the songs shouldn't need any sort of extra star-power to make it a success.
Actually a collaboration between the 2 for the movie could actually create something amazing.
J.LO gets kidnap and Rih is trying to get her back. They could easily make a cute song out of that.
She's posted a picture of her recording with Jim Parsons and she's been seen at Dreamworks studios.
