Sister’s wedding trip turned into 15 days of tears and loneliness

I (24F) currently in the US with my father, stepmother, and stepsister for my younger sister’s wedding. My stepsister flew in from another country—she doesn’t live with us in India. The wedding is being arranged by my aunt, who my sister recently reconnected with after 15 years. For context, this aunt is divorced, and her ex-husband is in prison. It’s been a complicated dynamic, to say the least.

Throughout this trip, my stepsister and younger sister have been making me feel awful. They’ve repeatedly made fun of my father or said and done things that have pushed me to tears. It feels like they don’t even realize how much they’re hurting me—or worse, they just don’t care.

Meanwhile, my father has been completely indifferent to my pain. He seems entirely under my stepmother’s control and doesn’t acknowledge my struggles at all. For the past 15 days, I’ve cried every single day. I feel so lonely and out of place here.

To make it harder, I miss my mother deeply. She was my source of comfort, and without her, I feel like I have no one to turn to. I’m at a breaking point and don’t know how to cope anymore. How do I make this stop? How do I deal with this overwhelming loneliness?

TL;DR: On a trip for my sister’s wedding, I’ve been hurt by my stepsister and younger sister, while my father ignores my pain. I feel isolated, cry daily, and miss my mother deeply. I don’t know how to cope.