Who needs to be present for Power of Attorney?


We have bought a flat in Mumbai in the name of my mom, my sister and myself. My sister stays in Mumbai, I am in Bangalore and my mom is in Kolkata. We need to take possession of this flat but my mom is not able to travel. Hence, I was planning to go to Kolkata, take power of attorney from my mom and then go to Mumbai to take possession (my sister is already there). Now, is it necessary for my sister to come to Kolkata when I am taking power of attorney from my mom? Note that my sister is going to be present in Mumbai during possession along with me.