Hi Pedro
The first step you should start with is better original picture. Your before picture is not the actual "before" picture yet an image that has gone through compression with artifacts while your after image does not have those compression artifacts. That would be a good starting point because many color and tone shifting techniques will make those rear their ugly head.
The image below is the blue channel only of your original image on the left and the after image on the right. You can see the hug amount of compression artifacts (blocking) on the left. So there is no way the left image is a starting point image from which to achieve the after image.
If you can provide the actual original "Before" image, then forum members might have a better shot at helping you.
I agree that the easiest way would be to ask your cousin for the exact steps they took compared to the trial and error approach to duplicate the same result via a forum member. Either way, starting from the actual original image is likely critical for a good end result.
Just my opinion of course
John Wheeler
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