Mostly likely not a true chimera, unless it is a male. In cats, the X chromosomes influence the coloring and it could just happen that the colorining of one of the x chromos is influencing one side and the other is influencing the other side. You see these split color faced cats fairly often. A true chimera would be much more rare.

Geneticist Virginia Papaioannou explains: This isn’t what I would call a chimera; it’s a striking example of a calico cat. It’s a fairly straightforward example of X-inactivation mosaicism, with the addition of a white spotting gene. All female mammals have two X-chromosomes. (Males have an X and a Y.) But both X chromosomes aren’t active: In every cell of the body, one of the two X chromosomes is inactivated. (That balances out the effect of the X chromosomes in males and females; since females have twice as many, it makes sense that half of theirs would be inactive.)

In a cat, one gene for fur color is located on the X chromosome. And in any female, expression of all the genes that are on the X chromosome will be “mosaic”—that is, half of them will express one version of the gene (e.g., black fur) and half will express the other version of the gene (e.g., orange fur). The inactivation is random. Here we are talking about the orange/black mosaicism, which is highly visible, but the same pattern will hold true for other genes on the X that have two different versions—or alleles.

It is a Chimera. According to Geekologie.com, a chimera cat is one individual organism, but genetically its own fraternal twin. The chimera is formed from the merging of two nonidentical twins, therefore they can be male, female, or hermaphroditic. Basically what that means is it was two embryos that merged together, making the cat look like it's two different patterns. Sometimes the difference is not as obvious as the face fur, it could be4 a hitchhiker's thumb and one straight thumb, eyes of slightly different colors, or completely undetectable.

@HippieChick58 thank you.