Why is it difficult? He died, and (hopefully) she has had time to grieve him. How long were they together?

Unless she is bringing it up every single date, I don't think it needs to be a problem. If you like her, you like her. Aside from wanting to take things a bit slower, are there any major red flags on her end?

I once dated a cute girl who told me on the second date she was raped by her stepfather in her early 20s. She was with a guy for 3 years before me and never told him. I asked her to confide something personal in me and she did.

Obviously I didn't hold it against her.. in fact, it was pretty clear she had dealt with it. Everyone has a past.