Interesting about perceptions of being called Isis.
As Chocolate mentioned, Isis is synonymous with our stretch of the Thames, here in Oxford, so seeing/hearing it everywhere is common and just part of the landscape.
(University's tech company/ local businesses' brand logos/ Oxford Uni's magazine is Isis etc. etc.).
Not the same as a child growing up with the name, though, I realise.
Maybe Lord Grantham's friendly old labrador in Downton is a nicer association? 
Part of me thinks, sod it, it's a beautiful name with a classical heritage, and the more babies named Isis the more it's 'reclaimed' from the terrorist association (at one point, the media started using "DAESH" instead of ISIS, specifically because the terrorist themselves hate that first term...wonder what happened to that?).
But then the actual lived experience for that young kid called Isis is what's important, not our adult ideals. Could go either way.
Situations where they'd be needing to wear 'first name only' labels (sports tournaments/ activity groups etc.) might draw unwanted attention in later years. Personalised t-shirts possibly wouldn't be risked.
Minor, occasional name-calling, shut down instantly by a few snappy comebacks from the Isis on the receiving end, is very different to (worst case scenario) sustained bullying.
Could very much depend on what environment we're talking about here, too.
e.g.
- Academic circles, classicist's daughter Isis: name probably doesn't even register within her peer group as unusual.
- More 'alternative' lifestyle, and/or musical/arty/theatrical/creative's daughter Isis: ditto.
Conversely, in an area heavily politicised, battling serious Islamophobia: pretty doubtful Isis is going to be chosen for anyone's baby daughter's name? And a child already called Isis moving into that area might not have the easiest time
Personally, I certainly wouldn't change an older Isis's name unless she was being made unhappy by it and the decision came from her.