I have been looking for single word that can be used in place of "fawn over"
I dote on Sally.
to bestow or express excessive love or fondness habitually (usually followed by on or upon):
There's also crawl.
Informal: behave obsequiously or ingratiatingly in the hope of gaining someone's favour. "a reporter's job can involve crawling to objectionable people"
synonyms: grovel to, be obsequious towards, ingratiate oneself with, be servile towards, be sycophantic towards, kowtow to, pander to, abase oneself to, demean oneself to, bow and scrape to, prostrate oneself before, toady to, truckle to, dance attendance on, fawn on/over, curry favour with, cultivate, seek the favour of, try to win over, try to get on the good side of, make up to, play up to;
informal: suck up to, lick someone's boots, creep to, be all over, fall all over, rub up the right way, keep someone sweet, sweet-talk, soft-soap, butter up, twist someone's arm; brown-nose; vulgar slanglick/kiss someone's arse;archaic blandish
This seems to be BrEng, it's not in Merriam-Webster