@Weecaza,
I'm an American, everything frightens me. Seriously, your future SIL sounds competitive and not very loving. I think it's a good idea to avoid her as much as possible. Women cannot dictate when other women can have a baby. For all she knows she may never be able to conceive. Our womb doesn't come with a warranty. Drunk or not, I think saying you would drag someone to an abortion clinic is deranged. I also believe that when people tell you they are capable of hurting you, believe them. And be very careful. I wouldn't let her give me a drink or an aspirin or a slice of pie.
I hope you think this over carefully, you may need to protect yourself and any future children from Auntie Batshit Crazy for years and years. I hope I'm overacting. But if you know any of her friends or neighbors that have known her longer, it might be helpful to see if they know if she is a mean drunk or a crazed lunatic. I apologize if I sound a tad hysterical, I just want you to be safe. Good luck with crazy SIL.