My sister doesnt want her baby

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My sister had her second baby this year and seems like she doesnt want him, so she left him with her husbands family. She said she went through (and is probably still going through) post partum depression from it. Today she just told me how shes had mental breakdowns from having to go get him because the family is sick. Shes beyond fustrated having to take him back. Then she started asking me if i would still talk to her if she gives him away. Im trying to be supportive but at the same time it just feels wrong that she just wants to give him up like that, but she absolutely adores her first born. Idk what to do. Any advice?