Evil (future) step mum

I'm going to try and keep this short but I need advice on what to do!
Okay so I'm 23 with a daughter and living with my dad because I've left my dv ex. I moved in with my dad temporarily (renting meant to he for a year) while he builds his house. He and my mum got divorced 2 years ago after 31 years of marriage and 4 kids together.
So almost 7 months ago my dad meets a women online. She lives 13 hours away interstate. He goes to meet her. They fall in love at first sight he tells me. She has been divorced and then seperated from her feonce. Been single for 5 years.
They see each other every so often and talk over the phone or Skype.
She came to visit after he had been with her for 1 and a bit months, this was the first time I meet her. As soon as I introduce my self and all that at he front door my dad told me that they were engaged. It hit me hard. I felt like it was an in the spot thing to tell me wasn't formal or anything and I had only just meet her. I'm the only one out of my family to meet her.
So as the time goes on I told dad how I'm worried about him marrying her so soon ( they are eloping next month some time) and that he has alot if money behind him. He just put her name on the deads of the house his building. This has never sat well with her she deleted me on Facebook and blocked me. I wasn't being a bitch just teying to make sence of it all. She has asked my dad to stop giving my sister money who lives in asia which he has now stopped.
But recently I had a miscarriage with my boyfriend, it was awful I woke and well you know the rest. She was getting ready to go out with my dad and dad saw everything. We had a cry. I didn't want to tell my partner as he had an important meeting that day. I told him that night though. But my dad told his women what had happened shes a nurse and I got no sympathy from her she didn't want to help me clean my sheets or anything like that. My dad told her he had to stay with me and he was going to take me to the dr. She didn't talk to me all that day as she couldn't go out now. That arvo I lost it at my daughter and yelled at her to be quite.( I just wasn't coping) I came out to where they were and she gave me the dirtiest look I have ever been given. If looks could kill I would be dead and she then turned he back to me. My dad told me she thinks I am borderline child abuser and she is worried for my daughter in my care!!
But my dad is sick. He just had a pacemaker put in he had iorn put into his blood today and he is crapping out blood all day for weeks. He is getting his bowl operated on next week. His not well. I'm worried she is after him for his money he has a lot behind him.
My dad and I just moved he got a place for me to get me into the rental market as i don't have any history and he will stay with me while his house is finished (hasn't even started yet!) And sign it over to me when he leaves and this will save him getting his own rental place and breaking the lease and loosing a bond. But he just told me that she will be moving in here once they are married. This was not the plan! I can't stand this woman I can't even look at her.
So what should I do? I havnt said how I feel as I know they are adults and its their choice I won't stop them getting married. I'm happy if he is but I'm worried. But I don't want her moving in with us. As they don't even know how long it will be for. It's a very small house too. We only just fit and our garage is stacked to the roof with stuff. My dad told me I can't buy the bed I have saved for for 2 years (its been a goal of mine since leaving my ex) as I can't store my bed now (as it's my sisters) in the garage as her lounge needs to go in there.
What do I say to my dad. I don't want to stir the pot. I don't want to up set every one. But it's not sitting well with me. Its keeping me up at night worrying about it. Ive tired to get to know her. I asked her to the movies a few times but she's never interested ive tried to go for coffee or just sit down and chat but nothing shes always busy or tied.
Sorry it's longer than I wanted. I need to vent a bit too! I don't want to sounds like a winging daughter or anything like thats I'm just concerned that's all.