It is nice that you have made a friend who seems to empathise with you, and help you through your grief. Only you can know, in your heart, if this relationship feels right.
I agree with the majority of posters though, and think that you would be wise to proceed with caution, and not be in a rush to move into a deeper relationship until you have had time to truly grieve your loss, and allowed yourself time to come to terms with what has happened - from what you say, your wife’s death is still very recent. There isn’t, of course, a “fixed time” for grieving, and everyone deals with it differently. If your lady friend is genuine, she will understand your desire to take things slowly, and won’t try to persuade you to move along too quickly. Enjoy the friendship you have with her, but be very cautious with any monetary and house matters for now.
I think most posters here are hearing alarm bells because of the big age gap. Just be wary, and listen to the concerns that your step daughters may have. They may be worried about this ladies motives and fearful that you could end up with very little to enjoy your later years.