From my own experience & what other artists told me:
– Never say “you have talent”. For many artists it translates into “you don’t work hard – just use your talent every time, have a free ride”.
– Your painting is very good: it looks almost like a photograph… (then whats a point of doing a painting???)
– Never give to an artist an artwork of another artist as a gift unless you are ABSOLUTELY sure he or she will like it. Just ask! We lot have normally very strong preferences in art!
PS. Personally I found patronizing words like “clever girl” be real killers…