Oh man, I'm late to the reply party, but I know exactly how your gf feels, because I am the gf with an allergy

I am lactose intolerant and have been dating my bf for about 2 years now. His family always gets this cake for celebrations and of course, it has dairy. For the last whatever years I've been fine with not having any cake

Until his brother chose to go vegan and suddenly all the desserts are vegan now

It made me feel so bad. It made me feel like my dietary need was less important than his dietary choice. It felt like I wasn't a part of the family or that I wasn't worth changing their tradition for, but they'd do it for one of their own family members.

As your duty as a bf, please please please do not let your family treat your gf like this. It sounds like you're already standing up for her, please stick by her and stand your ground.