Looked through your pictures again and had a second thought. It almost looks like it may be one or more old kimonos that were cut up to make a wedding dress. If so, the kimonos may be quite a bit older than the feed sack backing.
What you are calling collar pieces may be pieces from an obi or from a second kimono.
Please see if your friend will agree to an appraisal, it may be much more valuable than she realises.