She
Middle English: probably a phonetic development of the Old English feminine personal pronoun hēo, hīe .
wiktionary
From Middle English sche, scho, hyo, ȝho(“she”), whence also Scots she, sho.
Probably from Old English hēo, hīo, hīe(“she”) [1] [2] (whence dialectal English hoo), with an irregular change in stress from hēo to heō/hjoː/, then a development from /hj-/ to /ç/ to /ʃ-/, [3] [4] similar to the derivation of Shetland from Old Norse Hjaltland. In this case, she is from Proto-West Germanic *hiju, from Proto-Germanic *hijōf(“this, this one”), from Proto-Indo-European *ḱe-, *ḱey-(“this, here”), and is cognate with Saterland Frisian jo, ju, West Frisian hja, North Frisian jü, Danish hun, Swedish hon; more at he.
A derivation from Old English sēo, sīo, sīe(“the", occasionally "she”) is also possible, though less likely. [2] [3] [4] In that case, sēo would have undergone a change in stress from sēo to seō/sjoː/, then a change from /sj-/ to /ʃ-/, similar to the derivation of sure from Old French seur. [4] [5] It would then be cognate to Dutch zij and German sie.
Neither etymology would be expected to yield the modern vocalism in /iː/ (the expected form would be shoo, which is in fact found dialectally). It may be due to influence from he [1], but both hēo and sēo have rare variants ( hīe and sīe) that may give modern English /iː/. [4] [6]
etymonline
she (pron.)
mid-12c., probably evolving from Old English seo, sio (accusative sie), fem. of demonstrative pronoun (masc. se) "the," from PIE root *so- "this, that" (see the). The Old English word for "she" was heo, hio, however by 13c. the pronunciation of this had converged by phonetic evolution with he "he," which apparently led to the fem. demonstrative pronoun being used in place of the pronoun (compare similar development in Dutch zij, German sie, Greek he, etc.). The original h- survives in her. A relic of the Old English pronoun is in Manchester-area dialectal oo "she." As a noun meaning "a female," she is attested from 1530s.
