Jordan probably is too small for 2 Queens.. QN was Queen for like 20 years, she's probably still not used to not being Queen..
I remember hearing once that QR felt QN was getting too much media attention within Jordan and made sure that Jordan's media outlets barely covered Noor and did a lot more coverage on her.. she could be intimidated by Noor - perhaps felt overshadowed and her actions may have hurt QNoor..
While KH was alive - he was really the only link between everyone as well as the 'peace' between them.. it's possible that they never liked each other and once KH died, all the true feelings came out.
Also if it's true QN never got along with Princess Muna - Princess Muna apparently had QN cut out of wedding pictures from the weddings of Muna kids and supposedly tried to leave Noor out of 'family' events concerning her kids - then there were probably always problems and perhaps as an extension - KA never liked QN either and that could explain the rumored tensions..
While KH was very ill, there were stories of everyone behind the scenes trying to become 'heirs'... so surely if that's true it may have contributed to any animosity..
A lot of Queen Noor's 'projects' were also turned over to QR charity organization - now it's not even mentioned that Noor founded most of those projects - now it's always under the patronage of Q Rania or something like that...
With Queen Noor being so opinionated surely they've clashed at some point..
But like I said, who really knows other than them - and Queen Noor isn't talking.....
I did think though that at Prince Hamzah's wedding - Queen Noor was pushed to the side - she didn't seem like she was the mother of the groom - more like an extended family member... there was some article that said that she was kept as far away from Hamzah and Noor during the festivities.. that would have pissed anyone off - don't you think....