Where does “seua” come from?

seua (Catalan) comes from Latin sua, from Proto-Italic sowos, from Proto-Indo-European sewos, from Proto-Indo-European swé — self.

Ancestry of “seua”, step by step

Step	Language	Word	Meaning
1	Latin	sua	nominative singular feminine of suus; nominative...
2	Proto-Italic	sowos	his, her, its, their
3	Proto-Indo-European	sewos	(one's) own; his, her, its
4	Proto-Indo-European	swé	self