if by constitutional case to support the penumbral liberty you mean they base it out of previous supreme court decisions
the position of freedom of association has their position explicitly laid out in the constitution
i don't see how this should be a question. i know it is, but i don't see how it ought be.
she didn't want to be his florist for the wedding because she didn't want to be forced to participate something that she believes is wrong. forcing this would say it would better to force her to have to do something against her religion than to have the gays find a different florist.
consider: she could have supported their so-called right to marry, yet still had this position (that she personally would take no part). she shouldn't be forced to participate; she can do both, you know. Live and let live.