Im 24 my gf is 37 shes great love her with everything i have we have a really great relationship. I couldn’t ask for a better half. But...she has 3 kids 18, 12 & 6

Thwre great kids but very spoiled i dont really have to deal with it because we live apart i travel
For work so I probably visit them once or twice a month for 4-5 days this has been going on for a year now..whe im around for the most part there cool ..sometimes they act up but they’re pretty respectful kids but there is times when we go places and they want things they turn into apoiled brats and my gf instantly gives in..even at home she will ask them to do someyand they always have a response wither why? Or an excused on why it cant be done at that moment...when im there i back her up and say like “hey listen to your mom” or like “hey do it now no questions asked” type of stuff. I tried to tell her hey maybe u need to change this or that dont give into them dont give them what they want dont cater to them except for necessities like the baby dont need a toy everytime we go to walmart or we sont have to eat out everyday because your kids dont want home food...But when i talk to her about it she gets very defensive and says “is it affecting our relationship?” Or stuff like it works for me so dont worry about it..it gets annoying and i tell her im just trying to make them better kids when i correct the soiledness or when i tell her dont give into their shit. Im tired of it but i dont want to leave her..what do i do??? Is its always gonna be like this??? She had been single for a long time before me...also all 3 kids come from different dead beat days that have nothing to do with the children..is she just being over protective?? Idk im lost