Did i do something wrong !!!!!?

ME and my sister have not talked in 4 years we just started talking .she is younger ,I found out she has had 8 abortion 3 miscarriages,and thow tho pro life i did not let that bother me ,she never calls me and when I call her she wont return my phone call that day if I am lucky maybe the next day and no she dont work,I try to be so nice so I can see my nieces every time we do talk she is talking bad about someone usually her boyfriend see she has been married well going on her 2nd marriage in one year so I tried to tell her in a nice way to slow down so now she is waiting for next year she has 3 children right now by 2 different dads and just lost another baby to a 3 dad ,She never act like she care to have anything to do with me or my children my daughter is 7 and her is 6 and for a while there they were close now that ------is upset she wont let my daughter talk to her children nor me I still call everyday to ask if she would please just let my daughter talk to her ,s for what ever reason she is upset ,well she up set because i told her that she never calls me back and it not that she don't have the time she talk to her soon to be hub like 40 time a day ,and my question is should I keep trying to have a relationship with her it hurting my daughter she now ask why ----- wont let her talk to ------ I dont know what to say she is 25 and I thank she has never grown up but I would never tell her that for fear she wont let me see my niece,s I need help what should I do ,,keep trying it has been 2 weeks and no answer and no call ,,,not even to let the girls talk what would you do ? would you try to have a relationship with a family memeber you clearly douse NOT wont one with you