I wouldn't be upset about it. Older people have different views. It sounds nice of her. Your husband can be grieving a certain way. Give that time.
Not upset just feeling disconnected with him. I have panic attack all day. My heart aches
My mom passed away at the very beginning of my relationship with my husband (like within a month of when we became a couple) & I ended up asking him for a break for a week. He didn’t understand why I wasn’t so dedicated to our relationship when my mom had just unexpectedly passed away. Just know the way he is being towards you has nothing to do with you or how he feels about you. He’s grieving. Just try to be there for him, but also offer space if he needs it.
She might have just been reaching out to give condolences. Just be there to support him emotionally, physically and mentally while he navigates this difficult time. Cook up one of his favourite meals and give him a little hamper of his favourite things to try and cheer him up and show that you are there for him. People grieve in different ways and him distancing himself might just be his way of grieving. Him telling you about his ex's mum calling is probably him still trying to stay connected to you