Don’t know how to feel..

So we’ve had my dog for 8 years now, she was diagnosed with diabetes today, but that would mean injections of insulin every day, regular blood tests and check ups at the vets. So my mum thinks it’s best to put her down as she believes it would be cruel and not much of a life for my dog if we kept her alive. We’re all pretty upset about it, even tho we know it’s for the best , it feels like I’ve lost a family member and I just feel so numb and I don’t wanna talk to anyone...should I be feeling this way over a dog? I’m really gonna miss her..