Is it normal to do this ?

My friend is upset because she lost her fiancée two years ago. He died about a month before they're daughter was born. They were gonna get married that summer but they couldn't. She misses him everyday. She named her daughter Heaven because she knows her dad is there. Her middle name is Marie. It's really cute. She looks almost like her dad. Me and her have been together almost a year. She's still not sure she wants to be with me it makes her sad knowing her daughter never got to meet her father. Her daughter is only 2 she tells her about her dad a lot. She gets worried when she talks about him. She's worried her daughter won't understand it. She's still young. She's younger than me. I can't talk to her about it she'll be crying for days. She sometimes has nightmares. Is it ok to be with her and help her ? How can I help her and her daughter through this ?