Sorry, I'm on her side. Mailing it to yourself so you can later show it existed before a certain date makes sense. Anyone can backdate a manuscript.
Having been involved in writing, copyright and trademark disputes, I have plenty of experience with this.
It's more of an archaic copyright protection.
Before the advent of easy self-publishing, home word-processing and internet, if you designed a game then you needed a publisher. You'd send your idea in, the publisher would be kind, give advice then say "Sorry - not for us!" A couple of months down the line, the publisher would bring out their own version of the game. This happened exactly to a friend of mine.
Unless you pay for a good solicitor and have rock-hard evidence that a) you came up with the idea before them, and b) they have changed little from the first concept, then you lose. The ol' 'Post it to yourself, recorded delivery, leave unsealed' thing was a cheap example of a). Sadly, b) relies on court decision.
All this was before the available dissemination by internet.
Now, thanks to metadata, the creation date/creator thing is practically a done deal. The problem comes with the decision of how much does a creation need to be changed in order for it not to be a copy?
Advice is
always keep records and copies. Write the dated copyright* declaration at the start and end of any text.
It is quite true that as soon as you create something, be it a game, picture or writing, it is yours.
But you always have to state this. It is always about legal claim, not actual claim.
* Trademarks are a whole different game. You cannot just claim a trademark - you must register it. To do this, you apply to the relevant body (in the UK it's the IPO), they make sure no one has similar in a similar field of interest (known as a 'class') and, after announcing your claim for a short period, they tell you when you own it. Unless, you have registered your trademark, you cannot put the TM subscript in any publication. Oddly, you don't have to show it if you
have got the registered Trade Mark.
Trade marks are a nightmare if it goes to court, so the IPO really double-check if it is contested. This happened to us recently. We registered a trademark (back in 2010) for a dog treat called the Cherry Barkwell. Recently, a treat company that has been very successful in stocking a pet shop chain and was 'snapping up' and trade marking every name it could think of. The IPO paused their claim for the Barkwell - technically, we are asked to give permission and cede our rights to them. We didn't. We were asked to present evidence of our use (to the IPO) in the form of publications, leaflets, even photos of the name at markets and events. The rival company could produce no evidence to counter. We won. Thing is, they knew that if they went to the expense of a court they'd lose. It would've been cheaper to buy the title from us - we were open to the deal but it would be worth thousands to us. However, essentially they didn't want to pay anything.
