I am very sorry for your loss of Bella, and for your loss of your mother-in-law.
Bella will always be in your heart, even when you open your heart to another dog. I understand your concerns though. We went many years in between dogs because of life circumstances. Even with a 20+ year gap and a big change in breeds (from big Airedale to Yorkie), I worried whether we could love the new pup as much. Trust me, you will.
Each dog is unique and will capture your heart for different reasons. There might be similarities and there will be differences.
Best wishes.