Asking for support

I'm just looking for support if you have any negativity please leave it else where.

Me and my fiancé found we were expecting while I was going through finals during my last quarter of my Junior year. Our baby surprised us more than anything because we weren't really trying to get pregnant, but are blessed beyond measures with our bundle of joy and are beyond excited! We told his mother and then soon my family. At first his mom was all on board excited to be a grandma, kept threatening us if we weren't good parents she would try to take our baby away from us, constantly tell us how she wants to be in the delivery room, rub my belly, massage me etc. My ex roommate in college (my fiancé cousin) went to his mom telling her how the baby isn't my fiancé that it's my ex boyfriend whom I haven't spoken to in a year now, or our mutual friend I had a small fling with, but it never worked out. She then pulled me aside and asked me about it and I was very confused because I had no idea where all of this was coming from. My past is my past leave it there and focus on the now. I have no reason to lie to her or her son and I told her that and reassured her the baby is her son's. She wanted me to promise to her not to tell my fiancé what we talked about, but all I could see was worry all over his face when he asked me about it. I have nothing to hide so I told him. He confronted her and she got pissed off at me because I told my fiancé who has every right to know. Now she no longer talks to me. If she wants something done she talks to my fiancé to tell me things. If she does talk to me all she does is have an attitude towards me. She doesn't want a relationship with me, but expects to have one with MY baby. Right now we're all under the same roof due to me having one more year before I graduate college. She's made it clear when the lease is up she wants nothing to do with either me or her son. I'm trying not to feed into all the negativity, even when it gets really overwhelming I just hate seeing what it's doing to my fiancé. She's always up and down I know when our baby comes she's going to change again and is going to want to make amends, but I just don't trust her and don't want her around my baby when she's being flippy floppy because family doesn't do that. I'm just struggling to enjoy my pregnancy the best I can it just gets more difficult when she acts hot or cold.

I also have a question as to how you would address her smoking in the house.... my senses are x10 so I can smell everything it gives me migraines, I really don't want 2nd hand smoke, or for me to go into labor before I'm supposed to due to her smoking... or for my baby to get any kind of health problems due to her not being considerate...