As others have said, since a cousin is no less of an ervah than any other pinuyah, the same “lo siKrivu liGalos ervah” applies.
Actually, (barring niddah issues) neither is an ervah.
And lest you state that it is forbidden to talk to a cousin/unmarried woman because of one’s ervah status as a niddah), then it should be forbidden to talk to your own parent, sibling or child of the opposite gender, since they are intrinsically and permanently an ervah (unlike a cousin or otherwise unrelated, unmarried woman).
The Wolf