Telling my parents my gf is trans

I (24cis f) am home with my family for the Thanksgiving holiday and feel like it’s time to tell my parents about my girlfriend (26mtf) being trans. We’ve been dating for almost 2 years, and she initially came out to me in the early summer of this year. I want to preface with saying my gf is okay with me telling everyone in my life, as she explicitly told me so. She’s been out to everyone she’s close to since the early fall, and the only people I’m close to who I haven’t told in my life are my own parents. Knowing the way my parents operate, I wanted to be able to tell them in person, and prior to this week I hadn’t seen them irl since the summertime.

The prospect of having the conversation is eating me alive and I haven’t been able to unclench for the whole week I’ve been home. I have an older sister who I’ve already told, as I saw her irl around the time my gf was first okay with telling everyone she’s trans. My sister is usually non-judgmental when I talk to her about something serious, and the conversation overall went well with her.

I know my gf is okay with me telling my family, but I feel like if I share how anxious I am to tell my parents she’ll feel really awful about it in a particularly self deprecating way rn. She’s been having a horrible time already spending time with her own parents this week, as they say they still “love her unconditionally” but are refusing to accept her as a woman. I don’t want to add to her already difficult mental plate this week with my own anxieties, but I feel like for my own sanity this is a conversation I just need to have with my parents already. I’ve tried making a plan for the conversation with my therapist, but I just really don’t know how it’s going to go. My therapist also has no prior experience with someone in a similar situation to me at all, so that’s adding to my overall anxiety about the situation.

I’ve never even talked about anything remotely trans related with my parents before, and in the conversation I’d also be indirectly outing myself as being bisexual to them when I tell them my gf is trans and we’re still dating. They operate on the mindset of folks can do whatever makes them happy as long as they’re not harming others, but in other contexts I’ve found that same line of thinking doesn’t always apply to myself or my sister (i.e. they have different standards they hold us to vs. how they view others). I was also raised catholic (I now in adulthood am not religious) and while my parents are not the stereotypical catholic parents and don’t mindlessly follow every tenant to a t, I don’t know if this topic would trigger them to for some reason. I just feel very alone and don’t really talk to anyone else in my family aside from my parents and sister. So if I lose my parents, I lose a huge support system/chunk of my blood relatives.

I know my gf is going through a much tougher time, and I don’t want it to sound like I’m centering myself. I’m just freaking out and feel like I don’t have a reliable outlet to be anxious about how horribly this conversation could go. And I know it’s easy to be like ~fuck your parents, you’re an adult, etc.~ but I just generally don’t have a lot of people in my life I’m close to and a potential loss of some major ones is really just making me feel unwell to say the least. It’s a conversation I need to have and will have before I leave this weekend, I’m just terrified of the outcome.