I don't know about this half-golem theory.
Mind you, it seems reasonable, to some extent, on the other hand someone pointed in the comic thread that she hasn't any stitch (like all the golems we have seen), which is quite a good point.
The two sides seems more like blending, instead of one attached to the other.

Moreover creating a golem seems overall more expensive than casting a regeneration spell. (I give for granted that to make move a piece of dead flesh, or clay or iron, you must anyway bind an elemental spirit in it and do the usually steps required to create a full golem).

The only reason to choice such an outcome would be to gain the (honestly awesome) immunity magics related to golems. But at that point Serini shouldn't resent such a choice.

Are there any more ideas about what Serini could be?