Pre-tx here, but my clinic has warned me again and again that acute rejection is really common in the first 3 months and almost always completely treatable. Apparently the first months are actually the MOST common time to get rejection, even though it feels like it's too soon -- the lungs are still really sensitive and the body is kind of on overdrive. It sucks that your docs aren't really communicating, but for what it's worth my clinic has told me to definitely be prepared for a couple of bumps in the road like that...just thought maybe that would help put your mind at ease.
Lots of love and light and prayers to your sis and your whole fam! I hope you come through this quickly and easily!