Probably not. Let's have a peek at here PokéDex entries.
>Starry skies thousands of light-years away are visible in the space distorted by their intense psychic power.
>It can see the future from the movement of the stars. When it learns its Trainer’s life span, it cries in sadness.
Witches aren't know to be able to see the future by observing the stars, nor are they psychics; traditional witches use potions and spells (a la eye of newt) to observe the future, and from what I know of witch stories they don't see very far ahead. There is a distinct difference between psychic and magician, and it appears that Gothitelle is the former.
Fairy tale witches also aren't too sentimental.
"Goth" is also different from witch. The Oxford Dictionary defines goth like so:
A member of a subculture favouring black clothing, white and black make-up, and goth music.
There is nothing about goths that implies magic, although black clothing and play complexions are commonly associated with the modern-day witch stereotype. Gothitelle's colour scheme is almost exclusively black-and-white. No part of Gothitelle's design corresponds with the typical witch garb (pointy hat, wand, broomstick, warty nose).
TL;DR Based on my research, I can find no similarities between Gothitelle and a witch.
If you're looking for witchlike Pokémon, these may appeal to you.
![Mismag][1]![phox][3]
[3]:http://www.pokestadium.com/sprites/xy/mismagius.gif
[1]:http://www.pokestadium.com/sprites/xy/delphox-3.gif
