Who Is Right And Who Is Wrong

It is differing opinions. However it happens to be the elder sister's call as she seems to be the one expected to throw the party/ make arrangements. That has to be respected. When even the dad isn't coming, it's quite superficial for the younger one to land there with her inlaws.

The younger one could organise a family get together for diwali or new year. The younger one would be out of line to ask for more.

 

A small family gettogether in which only the closest one's are involved is not such an expensive affair.
A small pooja followed by a home-cooked lunch doesn't deplete one's bank balance.....By bluntly refusing the younger sister to be involved in the pooja, the elder one will forever create a rift between the respective families....

 

So this is gonna be a family pooja or something, in which the dad of the family isn't participating.
This Pooja is hosted by the elder daughter, who thinks it is unnecessary to invite more people this time. I think elder daughter is right here.

If younger daughter wants a family reunion or function, she can probably organize one at her parents' new home. As @guesshoo mentioned, diwali, newyear or a birthday party (parents's or her kids) or an anniversary or whatever it suits her time. She can think of a budget and list out the invitees. Remind her that she is supposed to organize the get together and spend on it, rather than just spending on the tickets alone.

Some people have way too much expectations...

 

I don't think it is a question or who is right or wrong. Each one is right in their own way but both need to adjust being a part of a family.
I think the elder one should invite the younger sister to attend. I think asking the younger sister to contribute to their parents instead of traveling is childish. The ticket amount can't be huge and will not help parents much anyway.

The younger sister can't pile own her ILs into a small family function. If she wants then she should share the expenses as well. If she insists on a family gathering, then she can arrange a function on her own like guesshoo said.

 

I think your colleague should have a conference call with both sisters and settle it (asking the younger to attend only by herself). Otherwise the issue will unnecessarily create a huge rift. It is an auspicious ceremony and so she needs to create a good atmosphere.

 

I'm sorry for the older one. She is being manipulated for a simple Pooja.

 

Since in near future such functions are not likely to be held...they should have get together with parents...both daughters and their respective families.
Perhaps they can pool money to bear cost of pooja..panditji dakshina...food.