My sister sold our Jaipur house without telling me. What can I do?

I just found out that my sister sold our family house in Jaipur without informing me or getting my consent. Our parents left it to both of us in their will. She claims she needed the money urgently, but this feels wrong. I only found out because the new owner contacted me about vacating the property. I'm shocked and feel betrayed. I haven't signed anything. Is this even legal? What steps can I take to challenge this sale?