Ha ha ! have to laugh at this dilemma (maybe I shouldn't !) but in my case I met my now husband after he had been a widower for, also, three years ! Not only that but he had built himself a villa in Spain where he had a lot of friends .......He 'sent' me down to Charlton to meet his sister and his dear old mum before I met him (long story !) ....they were lovely but very oddly they asked me if I knew him that well (?) (I didn't since I hadn't even met him face to face at that point (only speaking on the phone !) ......I then flew to Spain where we promptly got engaged ...he had arranged a party with all his friends ,,,,,again they were all lovely and accepting of me ....told me about the 'others' who had been out to meet him ...and again, asked me if I knew him that well ..... I met his friend's widow (the friend being the reason he had decided to move to Spain ...best mates since forever and work colleagues) ...she was lovely and really pleased for him (she had been a friend of his late wife most of her life ...having lived in a flat above theirs when they were first married in 1956 ....but again that question ....how well do you know him (?) ...then I met his daughter who flew out for a holiday and so I asked her if she had any objections to my marrying her dad as, I said he told me they had a wonderful marriage ....at which point she burst out laughing and said 'Did he tell you that ?' ....and explained about how their relationship was ...so much so that she had to move out and get her own flat !!!
Of course I didn't believe any of them .......after all, I had known him for three months and they had all only known him for 68 years (apart from obviously, his daughter, who had only know him for 38 years !!!....I found out why after a few months ....but hey, life is short and we have to make the most of what it throws at us ....so be happy for your friend hope the woman knows him better than I did my husband ,,,,,,,she may well be apprehensive about meeting you as you were close friends of his late wife, so be kind ! ask him if you can, about sleeping arrangements .....a friend and her 'friend' came to stay with us en route to visit his daughter in the Dordogne .....although we have 3 bedrooms, one is my office and is not going to change for anybody, so they slept in the same room which has two single beds ,,,take it or leave it ! We hadn't met him before but he was lovely ! a retired GP she had known from years ago and whom she re met when he was a widower and she retired back home to the UK after a career in Australia ....he was 90 (and drove all the way down here from the Isle of Wight) and she was then 77 ) sadly he passed away a couple of years ago so now she lives on her own in a retirement flat (now 81) ......
I would not hesitate to talk to him about his late wife in front of his new friend ,,I have photos of my husband's late wife in our house ...and why not ? They were married for 42 years and she is not going to object !people ask me why I have a photo of her ...but I say why not ? (I don't have any photos of my ex ...but then he walked out for the barmaid so it; different !)
We had a great time now having been married for 16 years ...still friends with his friends and a few old friends of mine have been to stay with us (mainly in Spain, where we had a lovely villa with a pool so they ostensibly came to see me but I feel probably more for a holiday !!!! but why not !)
You will only find out if you get on when you meet ...be accepting of her and you may find another true friend..she will never replace your dear friend of many years but she will always have a place in your heart and your memories ! Don't worry ...be happy ! [hugs]