But that world can exist: our opinions are mutable and it's quite possible to decide to like the play.

Possible, but utterly abhorrent.

whether you're willing and able to emphasize the positive over the negative aspects of something for her sake

Doublespeak for "doublethink, self-deception, and lies".

The conversation is also about asking for acknowledgement and approval for something she's worked hard on

One can acknowledge hard work without lying about outcomes. Approval given regardless of worth is meaningless and devalues itself (because if I approve of what you made, even if it's crap, then my approval is worthless, because it does not distinguish good work from bad, good results from dreck).

and probably partially identifies with.

Perhaps, then, she should heed Paul Graham's advice to keep her identity small; and apply the Litany of Tarski to whether the thing she worked on was good.

Please note that I'm not saying this is easy or obvious.

Sure, but something can be difficult, non-obvious, and undesirable.

Empathy is a difficult skill and requires training (or socialization), followed by practice and attention even for those to whom it comes easily.

I strongly disapprove of equating empathy with deception and tacit support for irrationality and emotional manipulation. They are not the same.