Oh come on guys, its very easy to judge isnt it?
But I can see that the DSD announcing her pregnancy at a sensitive time for the OP and expecting her fathers family to support her, with I assume old baby equipment and money, after having
cut them off for 2 years would be a bit galling.
And ok, so the OP is jealous, she is a human being and allowed to have unreasonable emotional reactions sometimes! She is venting on here, not at the DSD which is something atleast. The OP clearly has no understanding or experience of teenagers in the way that alot of the us have and doesnt understand how child like and vulnerable they can be.
OP, you are over reacting by saying that you dont want her around and in your house. It is, by virtue of being her fathers home, her home too. And her bad behaviour by cutting you off is the behaviour of a child, which is what she is and as the adult you need to understand that.
She is clearly living in a dream world of free houses and free money without giving a thought the reality of living with a small baby. It is very likely that, if her mother is a hopeless as you say, she will turn to you for help and your relationship may well change from wicked stepmother and feckless step daughter to one of 2 women offering support and friendship. Motherhood makes us grow up very quickly and the girl she is now will bear no resemblance at all to the woman she will be in a year.
I do wonder if this baby is a symptom of her feeling pushed out by your child. She estranged herself when he was born and now is saying "Look Daddy, i can do it too". If you look at it as a desperate girl wanting her fathers love and attention because she has had a difficult life with her mum then does that make you see her and the situation in a different, more compassionate, light?
I think that in your current circumstances, you would have to be a saint not to feel hurt and jealous by her pg. But dont allow it to take over your life and ruin your relationship with your OH as you resent his dd so much.