My fiancé hasn’t told his daughter (17 almost 18year old) were expecting a baby

So I will be 20 weeks Sunday . My fiancé hasn’t told his daughter who’s 17 will be 18 in October . Now she hasn’t spoken to him in almost a year . She had a hard time with him and his ex’s divorce and then when we got together . His ex was mad since I am so much younger than her is the idea I got . I am 30 she’s 45 or so I believe. I don’t really ask because she none of my business . My fiancé is 51 so the age thing is a big deal to his daughter and mostly his ex wife . Anyhow he has twins with is ex a daughter and a son . The son is very much involved in our lives . He knows we are expecting a baby boy in December . He’s hasn’t told his sister or his mom. I have a very good relationship with him I love him like he’s my own . Anyhow finally the other day my fiancé finally spoke to his daughter . They had a great talk and he said it went very well . However he tried to make plans to see her but she said she was too busy (as usual) . Anyhow I haven’t pushed the telling her I feel it’s his daughter and since she doesn’t really like me then I just stay out of it . But the further I get the more I wish he told her . Like I would be so hurt if my dad was having a baby and didn’t tell me . That’s my only reasons why I feel he needs to tell her but I don’t push the subject . But he can’t even see her in person let alone he’s lucky to get a text or a phone call . He Try’s but she never answers or reply’s back . Idk I just not really sure what to do I don’t want her to hate her brother . I also think about when he’s here and if she wants to meet him . Will she not want me around ? This is my first child and I tbh don’t know if I even be ok with her meeting him with out me there . I had miscarriage last year. Before while with my ex husband had Infertility issues . So it been a long road and this baby I just know I going to be over protective with I know I already am . Anyway I am hopping there are some of you out there that have some advice for me . I really not saying anything about the subject to him since it’s his Daughter and I have no relationship with her I feel I have no say . I just keep praying she will change

and be apart of our lives someday .

Update: Tonight he told his daughter she is very excited I am so happy ! She can’t wait to have a little brother ! Thanks for all your advice ❤️❤️🤗🤗