My sister and I stay with my dying Dad so he will not pass away by himself....scared and alone...he does not derserve to die along without a love one...we are both tired and beat down...we have one sister who lives close by to hospice but only comes in for a little while to visit and tries to take over ...example: he loves old country music and I will play for him..she shuts off and makes smart comments that he needs soft music that this isn't good for him etc...he hates ...we have ask her to stay with daddy so we can take a break but has excuses...we only ask so love one will be with him if he passes ...he is in hospice care...her daughter is 12 years old and mom has offered to stay with daughter which sister make excuse for not helping...she has always been selfish and all about her...she is sister by blood only...she has the personality that likes to start fights and hard to block out to a point I could go off on her. I try not to speak to her and pretend she is invisible cause daddy doesn't need to hear us fussing. So hard not to attack her. I am easy going but can take so much...advise needed.
On the occasions when she is there, if you are beginning to find her interference beyond unbearable, take advantage of the moment and go out for a coffee break or some fresh air. I personally found that was the only way to be sure I didn't deck my SIL or drag her away from my mother's bedside by her hair.
On the occasions when she is a no-show, though... a) count your blessings; b) let her be. You are all under terrible stress. No doubt she is doing her best in her own way.
Sending your dad much peace. God bless.