Difficult relationship and estrangement

Hi all! I’ve just joined (suggested by my mum) to try to get some peace of mind by telling people who might understand the terrible predicament I am in and asking for advice. I have an adorable granddaughter aged 2. I adore her. She is the daughter of one of my two sons who have become very involved in their own lives and rarely contact me. That’s really another matter though. My problem is that my granddaughter’s mum has taken great offence at little nuggets of advice I gave her in the past. Once I was aware of her ‘feeling livid’, I have been super careful to ask her permission for absolutely everything I do or buy and I never offer advice on anything. Her own mum gets to keep my granddaughter overnight, sometimes for several days while they are away on a break yet I’ve been told not to even ask as it ‘puts (her mother) on the spot.’ I am beyond heartbroken but have to play the game and accept any little bit of time they allow me just so I can see her. Every visit is arranged so my daughter in law can be there so it feels like a supervised visit. I have done nothing but be enormously kind and generous but it isn’t getting any better. I have just had six weeks holiday. I was offered a visit from her at the start and now a visit before I return to work, again with my daughter in law in attendance . My side of the family are furious but keeping it quiet so I get to see this wonderful child. I don’t know how long I can keep up the pretence though as it is very stressful. I’d be grateful for any advice. Thanks x