Why is the photo of the person taken by the SLR flash golden?

There is glare in your photo, so that the whole photo is "polluted" by glare, especially in the upper left corner. Glare will affect the image quality, just like being covered with a layer of golden fog.

I think there must be a bright yellow light source in the upper left corner, and it enters the lens obliquely. It may be a street lamp. Most street lamps use high-pressure sodium lamps, which is the color. Using a hood can partially improve the glare problem, but attention should also be paid to avoiding it when composing. ?

Although it is not a white balance problem, it can also be corrected by white balance. I fixed it for you ... Besides, the model is a beauty.