The "Charmed" actress's relatives all swap gossip in the messaging service but she's been left out for years - though she said that could be because she isn't a "phone person".
"I don't do WhatsApp groups - I found out my whole family is in one except for me. So rude! It's been going on for years. It's probably because I'm not really a phone person or because I have a weird family," McGowan told Grazia magazine, reports femalefirst.co.uk.
She also "doesn't really care" about using social media to see what her friends are up to as she'd rather just catch up with them in person.
She said: "I hardly ever scroll through Instagram. I don't really care about other people's feeds, I care about them in person."
The 46-year-old actress often suffers from nightmares but has found crime scene re-enactment programmes help soothe her when she wakes up anxious and can quickly get back to sleep.
"I have nightmares often, like, three times a week. I wake up covered in sweat and it takes a little while to calm down. "Sometimes I put on a show called 'Forensic Files' - it's crime scene re-enactments, with a really soft voiceover about death, and for some reason, that calms me right down and I go to sleep," she said.
( With inputs from IANS )