Suburban slang (see “being a Karen,” and “being a Linda”) for (a) constantly being mean to your spouse when unprovoked ; (b) appearing angry with your spouse in public for inexplicable “reasons;” or (c) intentionally knit-picking your spouse in public, primarily because you believe it’s funny to emasculate men in public.
You were being a Heather when you made fun of your husband at the party last night - he was so embarrassed when you said he didn’t know how to fix anything without paying a handyman.