Just wanted to say that life in a foster home can actually be alot of fun, and a relief for many children. No doubt many of our former foster kids had a great time here, and we loved having them
All situations are different.
You did what you knew to be right, you put the childrens well being before your own needs. There is no guilt for you to feel, in fact it is the opposite. Your sister should be embarrassed you needed to do such a thing.
I am proud of you, and suspect your sister may thank you one day