Human Chimerism...

[asplundii]

I imagine it's impossible to breed this snake if it is indeed true chimerism, the DNA would be all messed up or if it does breed you would get one or the other genetic material, it's not possible to reproduce this in the offspring.

It is completely possible for chimeras to breed. Nick Mutton has a chimeric carpet and it produced a perfectly fine clutch, all of which hatched out.

It seems you missed the part in the article that said her auto-immune disease is caused by her having 2 sets of DNA and 2 immune systems, so it is inherent in being a chimera to have this problem.

False correlation. Just because this one woman, who is a chimera, developed an auto-immune disease does not mean that all chimeras will necessarily develop auto-immune disease. It is not an inherent condition of chimerism.