Use of schatje
Could schatje be used to indicate a friend (both women)?
in english I would say "Are you ok honey/my dear?" but I am afraid that the expression mijn shatje would be unappropriated to indicate just a friend. Could someone mention to me common nice words to indicate: a female friend (which is not a best friend or lover) ; a child; a male friend (which is not a best friend or lover).
Mijn schatje or mijn liefste/mijn lieveling (my darling/my sweetheart) should be reserved for your lover/wife/husband, not a friend. If you're very close with your female or male friends, you could probably call them schat or lieverd. Saying something like "Gaat het goed met je, schat?" (Are you doing okay, honey?) would be acceptable between close female to female or close female to male friends (but not male to male generally, unless they're lovers).
Adult female friends might also use words like "meid" (girl) to address each other, like "Héé meid, heb je This Is Us gisteravond nog gezien?" (Hey girl, did you happen to watch This Is Us yesterday evening?"). A male might address a close female friend (or his younger sister(s) or daughter(s)) with meisie or wijfie. Parents will call their children "schat" or "lieverd," and if you're an aunt who's close with her younger nieces and nephews, or an uncle who's close with his younger nieces, you could use those words as well.
Male friends don't usually use such terms of endearment at all to address each other, other than maybe saying "Héé kerel...." (Hey fellow/chap...").
I hope this helps you!
'schatje' is (imo) used in a more romantic manner, but if you want to call your friend honey or dear, it's better to use "schat" (without the 'je').
I think you can use "schat" for practically everyone. (although I would not recommend calling your parents or your grandparents "schat")
A different word to call someone, is lieverd, which can be used platonically and romantically. (again imo)