I think it's possible your friend is silent because she realized she stuck her foot in her mouth after discovering your boyfriend's race. She may simply be avoiding an uncomfortable conversation or yes, simply avoiding you.

This is one of the realities of interracial dating and you'll learn how to handle it along the way. Best approach in my opinion is to simply tell her your observations regarding her behavior toward since that statement and if she's uncomfortable with you. It may give you an opportunity to start a productive dialogue with her. If she gives you the sulky silent treatment then consider yourself lucky she no longer has the opportunity to spew her poison in your direction. Hope you find a new cycling buddy if the latter is the result.