So here's the story:
I got engaged to my FI last December, the wedding is this December (five months from today). At that point, we had been dating for 15 months, and unofficially living together for awhile. The thing is, we're both in college. We're both 20, will be 21 on the wedding date. My parents are both insisting that I am too young to be married. That's fine, I can respect their opinions, but I disagree and want to be married to my FI before we move away to grad school next spring (also, my dad married my mom at 19, so he can't really talk). I am financially independent, and my FI and I have our own apartment and pay our own bills, so it's not like I need my parents to support me, at least financially. My FI and I are also covering the costs of the wedding, so I'm not asking them to pay for it.
The problem is, my mother has (in my opinion) severely overreacted. My dad said I was too young but it's my decision, but my mom has started refusing to acknowledge that I'm getting married. She tells people I'm not getting married until March even though I told her it was December. I called to ask her her family's addresses so I could send out save the dates and she refused to talk to me. This was two months ago. She talks to me about other things, but if you bring up the wedding she goes beserk, yelling and refusing to talk about it. I talked to my dad about it and he said he honestly thinks there's a chance she won't show up to the wedding. Also, I can't send out save the dates because I have no way of getting them to her family, and I wanted to send them out two months ago. However, if my mom is not going to attend, I will not be inviting her family (with whom I am on poor terms).
I don't know what to do because I literally cannot talk to her, every time I try she shuts it down. I need to at least get the save the dates out soon, but I don't know if I should send them to her family if there's a chance that my mom won't come, and I can't even send them until I can talk to her about it.
Please give some advice!