There is no time to wait for the step parent adoption. And the grandmother has no rights to the child. If she tries something though, I would highly suggest you get an attorney. Where is the biological dad? If he does not consent to the adoption, you may have to wait a year to be able to terminate his rights.
To add to Mr. Schneider's asnwer, where is the biological father. He will need to be notified. Best of luck to you.
This information is provided as a public service to provide a general answer and should not be relied upon as legal advice.