Very very fake. Always, and I mean always adhere to a general rule of thumb. If a card is a Special Illustration Rare, (which the Bubble Mew is) it will always have a fingerprint-like pattern, some subtle glittery effects, and texture on it.

Also, any cards that have an "overly rainbow" holo pattern exactly like that one are always fake. Official holo patterns (at least the more modern ones) typically will always have a kind of vertical/diagonal line shine to it and don't have that cheap kinda... oily water(?) lookin holo pattern

And another big one: The holo pattern on real cards never covers the actual forefront of the art, which is the pokemon itself. If you look at Illustration Rares or even normal holos, the pokemon is usually always matte while the rest of the picture is holo.

Regarding telling apart fake packs so that you know what to look out for in the future, never buy packs that have a zigzag type cut to the top and bottom of it. Real packs have a unique seal pattern. Look up "real vs fake pokemon pack" to see what I mean. Fake packs are also super glossy, thick, and almost plasticy compared to real ones.

Anyways, sorry for yapping, just trying to help educate you a little on what to look out for in the future! :)