Update: Jim Harris of the Green Party agrees that an ex-Green made the website, and has issued an apology..
More checking seems to confirm that adrianecarr.ca, the website that is currently hosting a message stating that Green Party candidate for Vancouver Centre Adriane Carr is endorsing her likely opponent in any upcoming election, Liberal Party incumbent Hedy Fry, is still the property of Webtide Internet Solutions, which in turn suggests that the registration information showing that former Adriane Carr supporter Jayun McDowell is the owner of the domain is in fact true.
A whois lookup of gowebtide.com, the domain for Webtide Internet Solutions, Jayun McDowell's employer, shows that adrianecarr.ca shares the same IP address as gowebtide.com and shares the same mailserver as gowebtide.com.
That means that this site is under the control of Webtide Internet Solutions (unless it has been hacked, of course). That means the registration information that shows the owner of the domain as former Adriane Carr supporter Jayun McDowell is likely to be true as well, given that the registration information provides Webtide Internet Solutions phone numbers and addresses as part of the contact information.
So I would ask Jayun McDowell what he knows about the Hedy Fry endorsement, assuming I was investigating this for the Green Party, and I would probably not focus on Hedy Fry or some sort of Liberal Party dirty tricks campaign.