See "A researcher has wrongly claimed co-authorship of my publication" in https://explore.researchgate.net/display/support/Authorship for instructions how to correct this. But unlike this help page suggests, most probably it was not the other author herself who wrongly claimed authorship, but ResearchGate's automatic algorithm wrongly identified her as co-author and assigned your publication to her profile. This is a frequent problem in ResearchGate in case of similar names.