Wow....your light at the end of a difficult journey. Enjoy it, these things always happen for a reason.
Having suffered a MMC in January, after 10 years of nothing happening. (Grade 4 cells too...and alot of treatment required) I can sympathise with your friend.
It is hard to hear others are pregnant, but at the same time you genuinely are happy for them. Its not their baby you want, its your own.
My next door neighbours who are in the same situation as us, older kids also found themselves pregnant. She delivered a healthy boy last week, at that stage i hadn't got my bfp, and it did for one split second tug at my heart, but I was okay. Your friend will want nothing but the best for you, considering you've had a pretty difficult time yourself x