You are definitely not a monster. It could just be that you are still on auto-pilot and it will hit you later or it could be that you knew for a while what was happening and had already done a lot of your grieving. I think it was a bit like that when my dad died. I didn't cry or feel anywhere near as sad as one is supposed to and it wasn't that I didn't love him. I was really upset a few years earlier when he had a serious diagnosis and I feared we might lose him, but I think by the time he died, he was in his 80s and had been unwell for a while so I knew it was coming (didn't expect it so soon, but I knew he was in his last years) and was somewhat prepared for it.

I don't think there is a "right" way to feel about these things. It sounds like you were there for your mum when she needed you which makes you a loving daughter and a good person.

Thank you [@MargaretMary]‍ and I'm sorry to hear of your dad's passing! 
Yes there's definitely been a lot of grieving in the 6 months whilst she was here, I cried a lot, sleepless nights etc which is why I assumed I'd feel worse when the time actually came to say goodbye.....it feels like she's in hospital or on holiday still, we picked up her ashes yesterday and she's sat behind me and still I can't compute that it's her. 
 

I really appreciate your helpful reply, thank you! 

Thank you [@MargaretMary]‍ and I'm sorry to hear of your dad's passing! 
Yes there's definitely been a lot of grieving in the 6 months whilst she was here, I cried a lot, sleepless nights etc which is why I assumed I'd feel worse when the time actually came to say goodbye.....it feels like she's in hospital or on holiday still, we picked up her ashes yesterday and she's sat behind me and still I can't compute that it's her. 
 

I really appreciate your helpful reply, thank you!