I'm in the USA, and I can tell you that this photo, while probably a pleasant memory for your mom, certainly wouldn't be accepted as a passport photo here, either.
For example, the US Passport Office have very specific rules on quality, how recently the photo was taken, and almost no Photoshopping is permitted. In fact, they are enforcing these rules more strictly in recent years because of the terrorism threat, illegal immigration, etc.
In fact, even if happens to be accepted by the passport authority in your country, if it doesn't match up with what the immigration officer sees when she tries to enter another country, it could cause her to be pulled aside and questioned, and, in the worst case, refused entry. Is it worth risking this?
I'm not sure where you are located, but in most places one can get a new photo taken for a very modest price. She shouldn't be concerned about "looking good" when it comes to ID photos. None of us ever do, LOL. Just give them what they want: a new, higher quality photo that meets all their requirements.
HTH,
Tom M