Your sister has several different avenues and different things to think on.
I am adopted. And my daughter is too........ We went through several adoption attempts over the years until Brianna.
There are books you can read on the subject, that may help.
Some of things you need to think about are --
Do you want an infant only? If you are willing to look for an older child, what is the age cut-off?
Would you consider a child that has either physical or mental or emotional problems? (This takes a very special person, so don't be embarrassed to answer honestly.)
Would you consider a child from a different ethnic background from you? (There are many African American children available through Children Services. There are also children in other countries available through International Adoption Agencies.)
If you are looking for an infant, how open of an adoption are you okay with?
I recommend that you (your sister) write everything down. These are questions that you will be asked over and over again.
Feel free to PM me.
MA