My girlfriend wants a full length mirror to hang on her bathroom door.

She wants the mirror on the inside or outside of the door?
If inside, I would like to see suggestions too because my concern would be about mold growth between mirror and door if placed on the inside facing into the bathroom.

Weight is your only big concern. A big mirror (big enough to cover the whole door) will be pretty heavy.

There are gazillions of mirrors out there designed for this purpose - Target, etc. etc.

If you don't want it to be so visible you can consider inside a closet door. (All entry hall coat closets should have one on the inside of the door, IMO.)

I can think of 2 things to consider.
1 -Is it a solid or hollow core -- this makes a difference in what type of fastner you use, and if it's heavy , does the door have 3 hinges instead of 2
2- Is this her house or an apartment -- management might not like it

And of course like mentioned or need to get permission -- ot on the inside ( fog, mold )

Based on some of the posts in recent threads from the Board's self-labelled Alpha males, I think the consensus advice will be to dump her for being high maintenance.

The first part of being alpha is thinking alpha. Location also helps.

I can only imagine what type of research the op does when faced with an actual decision. 

Location? As in sitting in front of a computer monitor? Not directed at you, by the way.

Haha nah, it was more a dig at myself for my "location."

No worries, I'm always game to be taken down a peg.

I have one of these in my bathroom.

http://www.target.com/p/over-the-door-mirror-bronze/-/A-13589442?reco=Rec|pdp|13589442|TargetClickEV|item_page.vertical_1&lnk=Rec|pdp|TargetClickEV|item_page.vertical_1

$25. Takes five minutes to install. As I recall it comes with all the necessary mounting hardware. It's really not a complicated issue.

That's such a beta thing to say bro.

The only reason she would need a mirror would be to look nice so that she can cheat on you.

 

You caught me, Badandy.  So, which of the 25 rules on being an Alpha Male did I violate to tip you off?  http://www.traitsofthealphamale.com/77/25-traits-of-an-alpha-male/  Maybe I need to spring for the classes at the bottom of the page.

Sounds like you should start your research by doing a google search for "girlfriend bathroom mirror."