Underweight

J+L2006

I asked about this a long time ago, but I'm still concerned. My neice was born on cinco de mayo weighing I think 8 lbs 5 oz (SIL removed the post from fb). At 3 weeks she was down 20% and hadn't seen a pedi. I called concerned and she set up an appt, only to cancel a few hours later. We haven't gotten along well and we are not on the same page with parenting styles- so I took this as a polite way for her to tell me to back off- so I have tries to stay out of it. Well I found out today from MIL that she is now still not quite 9 lbs and is almost 8 weeks (still no pedi visit, and I am out of the loop if the midwife is still involved). I am distraught- but don't know what to do or say. MIL has made it clear that she won't say anything, and SIL already ignored me. What advice do you ladies have?