Mother's day issue

I need advice, I don't know if this is me being dramatic, or if I'm rightfully upset.

For context, I (18f) have two older sisters. We see my family pretty frequently, as we live in the same town. We are very close with most of them. The only grandparent I've met is my grandmother on my father's side. My sisters are both in their early or mid-thirties. Why that's important is that means they have so many memories with our dad before he passed, and with our family that I don't have. Which, good for them, but it still hurts sometimes.

My oldest sister, let's call her Holly, is like I said earlier, very close with the rest of our family. They bend over backwards for her, which in and of itself isn't what bothers me. She lives with me and my mom, so she and I go visit them all the time. And sometimes it seems like they don't really acknowledge me. I've always been quiet and didn't like being touched as a child (I believe due to some trauma), but I've been in therapy and have been way more open and sociable. But I feel like that early stuff caused a slight disconnect. So, I constantly feel pushed aside or unacknowledged.

This happened a few minutes ago -

I was sitting in the living room, working on some Latin. My sister and my mom are going somewhere, I ask where. They tell me they're "going to see a man about a dog." The usual joke. I asked if I could tag along if I finished before they had to leave. No.

Holly then tells me that they were actually making plans for our grandmother for Mother's Day since we don't know how long she has. I asked why they hadn't told me anything about it, and she said for the same reason they didn't include our other sister. (She blocked everyone and told them not to reach out, except us. I literally have no idea what this comparison could mean.)

Do I push back and ask what that's supposed to mean and why i wasn't included? Or should I just let it be?