Assuming the flash is normally automatic TTL mode, so that its light is metered to take care of itself. Then TTL is metered so that the TTL flash power level is adjusted to provide a correct flash exposure.
We don't know which camera we are discussing (brand, and a compact or DSLR, etc?), but speaking of camera more sophisticated than the minimum, then indoors without flash, the ambient exposure of course typically may need a slow shutter speed. But when flash is used, most cameras will enforce a Minimum Shutter Speed With Flash, often about 1/60 second (because we are using flash and don't need slower). If metering without flash was say 1/8 second, then this ambient will be underexposed three stops at 1/60 (but not to worry, we are using flash instead). This faster 1/60 limit is not about any proper exposure, it is simply an arbitrary minimum limit, because we are using TTL flash instead (the camera gives up on the dim ambient, and plans to use flash instead).
Check your images EXIF to see what actually happened. It will show all details. I think you will see a slow shutter speed and a faster shutter speed, for the reason just above.
So this is no concern if the flash is not used, when the example 1/8 second will be used as was properly metered. But the camera does not know that you used the flash, but blocked its light. So you got a faster shutter, about 1/60 second (insufficient for ambient), but you blocked the flash (insufficient for flash). Don't do that. :)
Which image is most accurate is of course the one with the better actual exposure, the one with the better light that came out to be the best picture