Like Emz said it is early days yet no matter what age we are losing a parent, the person who has been there all our lives is devstating as the foundations crumble beneath us.
I think for you a double whammy with your children leaving home imminent.But when you thinhk about it we all left home ourselves and even though the bond with your mum probably changed at that time it wasnt brocken, we still needed them, still loved them just as much and so our children will do the same. You were still close - maybe even closer than when you lived at home,as the domestic tensions and roles no longer applied - getting through those adjustments is the hard part but you will.
When my husband died my two daughters had left home long before but lived close by until the previous six months leading when both moved away - one of them right across the world -the other closer but not close enough for that every day contact we had previousely had - my mum had also died a few years previousely.
as a carer one way or another since i was 15 i had no other meaningful role to fall back on- sure i was working but it wasnt really serving anyone - I felt like there was no purpose to my existance whatsoever for quite a long time and finding something seemed like plaiting mist - but gradually i have learned to be independant, fill that time, and find ways to help others - whats app has helped a lot with being in touch with the girls -and i get to travel too which is fantastic - i miss my daughter abroad of course i do but i wouldnt have been able to travel the way i can now if she hadnt gone - so sometimes things like the kids leaving which feels like a threat when it happens can ultimately be an opportunity as well.
Even though she had died before that time in my life, my mum was behind me pushing me forward - by the way she had lived her life , by the strength she had showed through some awful times of her own . by her generosity of spirit, kindness, compassion, the ability to forgive and her optimism and humour, and of course i still miss her physical presence as i do that of my husband and others i have lost -but i have never really said goodbye and i never will - because they are still in some way a part in everything i do still guiding me in my heart and my head.