Hello, I'm Dr Deb and will do my best to help you today.
This is a tough situation although I can see both sides: I can certainly understand why Indigo might be upset. On the other hand, I can also understand why you'd want to bring these kittens into your home and provide for them.
I do have a few questions to ask first if you don't mind:
1. How long have the kittens been in your home?
2. Did you completely isolate them so that Indigo had no contact with them?
3. If so, how long did you keep them separated?
4. Did you slowly introduce them to each other after the separation period?
5. How does Indigo behave towards them? Does she run from them or hiss/growl or attack them?
There may be a slight delay after I receive your answers since I have to type up a response to you. Thanks for your patience. Deb