For #75148 specifically, I know there have been multiple counterfeit releases. There are at least three or four different colour variations so you can't just go by what PinPics is saying.
My own pin says "Hidden Mickey / 4 of 5". In this case to spot fakes, the best places to look are the eyes, tongue, background and the Mickey head icon. Any colours that are obviously off, or a Mickey icon that's distinctly misshapen, is an indication of a fake. The eyes should be yellow, not greenish. The tongue should be pink, and obviously lighter than the background, which should be a very deep pink, almost purple.
Some fake releases of this pin have the tongue pink, and the background a very similar shade of pink, while on others the background is a very dark purple. If you have the "Two Tiny Wings" (#75145) and/or "Horns of a Steer" (#75147) pins from the same Hidden Mickey set, the background of the heart should be the same, or very similar to the backgrounds on both those pins.
Hope that helps!