I did all the stuff for the father to where they want me to warn desdemona but when i go to talk to she just says normal things like she is having a normal day and it wont let me go into dialogue with her at all to try to warn her i need help on if there is anything i should do I really do not want to have to start over or kill her which would be the next task because i want to stick with the railroad.....
Side note:i killed all the brotherhood of steel on the blimp and elder maxson and even paladen danse....
PLEASE HELP!!!!!!

From what I can tell, taking out the brotherhood on the Pridwing seemed cause it. I reloaded a save that wasn't too far back in the story, but was before I had taken out the brotherhood to see if that had something to do with it. When I got back to the point that I had to warn Desdemona it worked fine. If you have a save before the point you took the brotherhood out I would recommend reloading to that point and try doing it without taking them out and see if it will work for you.

Hope this helps!

Same problem here. Since I was enemies with the Brotherhood already, I decided to take them out at the airport and their airship to gain some XP. This is annoying because now I assume I am forced to kill Desdemona to continue the game which is not the path I wanted to take. And unfortunately, I do not have a recent save before I did that (hours prior).