// You shouldn't be working around a principle, Jim. If it's wrong for one it's wrong for all. //
I'm not working around it. In both my examples there are, in effect, two jobs on offer at both places: For the case of the Sabbath "exemption", there is one position that requires a Saturday shift and one that does not; for the case of refusing to sell alcohol, there is a position that requires directly selling alcohol and one that does not. In such situations, the person seeking the "exemption" merely takes the second position and not the first.
If, however, the second position were not available, for whatever reason, then absolutely the person shouldn't be offered an exemption, or, on discovering that they are refusing to fulfil their duties properly, they should be sacked.
Applying this to the present case, in the limited case that she hadn't also made and reaffirmed homophobic comments etc, then if two parts are available, one requiring an actress to play a lesbian against their wishes and one that doesn't, you could simply offer the second part.