Sounds to me like this young mom has the "I am left out" baby blues and doesn't have the maturity to know how to deal with her multiple insecurities rationally for the best interest of all...keep showing her consideration and love and maybe try to include her in some family events on occassion - sometimes feeling like everyone wants "the baby", but no one wants you, can bring more emotional upheaval in a life that has faced multi-years of rejection from many.

By loving the "unloveable" you will ultimately have what you desire - more time with your grandbeauty.