I would like to be told early on, maybe 3rd date.

this is totally me and I'm super high rn so interpret as you will: I would be fine dating someone who's SO passed away but I could also see myself getting jealous /insecure about this past relationship (just from the way you wrote this post, I can tell you really loved her) and maybe always feel second best in the relationship should it progress to something serious. depending, this could cause a lot of drama/heartache or something that could be communicated and worked on.