Mother in delivery room

Hi ladies I’m due the beginning of august with my first child and since the moment I knew I let my mother know how important it is to that she is here for the birth of child for support and a time to invite her into my life for such a blessing and life changing experience... she lives on a semi truck with my father and I invited her to stay with me the month of July and August to help me and meet her new grandchild. Well today my sister calls me and tells me that my mother promised her that she would be taking my nephew on the truck with her for a mini vacation in July for two weeks *keep in mind I’m due in the beginning of August so baby could come anytime in July but I hope to make it 40 weeks. So there is a chance that she will not be there for the birth of my first child and I’m very upset about but everyone thinks I’m just being hormonal ..... my sister said it’s my fault cuz I moved which I do not agree with since I invited my mother a month in advance .. what do you ladies think?