I would like to pet this creature

Good it should be pet.

Even a Space Marine can not resist the cuteness of a cat

Tru that brother

I'm surprised that there isn't a major chapter with cats as a major symbol (That I know of). The closest we have to that is The Sons of Horus, due to Egyptian mythology being an extreme influence on their design by GW. The designers/writers could have easily incorporated designs inspired by Bastet, but it makes more sense for them to be based on Horus (The Egyptian God) due to the Primarch being named Horus.

Isn't their a cat girl regiment in Warhammer 40K?

Yes they are called felinids

Interesting