My mother considered gambling as playing with money.
She's correct, but whether that's an inherently bad thing is another issue.
My opinion is that gambling has its dangers of course, but any winnings you end up taking away from the casino aren't dirty at all. Drug money I would consider dirty. Money that was gained from a robbery or some other theft, same thing. Gambling winnings? Hey man, you earned that. I'm aware that there are a lot of members in the gambling section from eastern and other countries where perception might be different, but if you asked anyone in Las Vegas this question they would laugh in your face or simply ignore you with a disgusted look on their face.
Gambling money turns dirty if this was illegally acquired and doing this in countries that prohibiting gambling is also a dirty money
Not so sure about that. Some laws are meant to be broken, and even if someone won a jackpot in a country in which they were not supposed to be gambling I would still consider that 'clean'. Nobody was harmed, therefore no foul.
I also think that when people are religious or fear God, they will stay away from things called gambling and say it's haram or hot money.
You do realize that many people who believe in a god are not muslim, right? And personally I don't think if there is a god that he cares about someone winning some money playing cards, slots, or whatever. It's a pretty small sin, no?