Here is what I did

I posted an update on FB that I'll be deactivating my account (so MamaGrinder and RL friends wouldn't think I died or something).

The I waited three days. Logged on, deactivated the account (took a minute) and since then I haven't been on that site. I guess deleting works too but it's not like they'll delete the old data - even if they might say they are.