(cis woman) Worried that sexuality could ruin relationship with mom?

I wasn't sure if I should put this in coming out or family/friends, but this seemed a bit more fitting because it deals with coming out.

So I've been totally out as bisexual to myself, one irl friend who follows me on tumblr, and on tumblr since about February 2013 after questioning my sexuality for 6 years (currently 19, almost 20). It's not so much that I had a whole coming out speech as I just have a bi pride sticker on my blog and have made a few posts mentioning it. Making a speech or straight-up telling family or friends really isn't my thing as I'd feel awkward, so as of right now I'm sort of planning on it just happening where in the future I bring a girlfriend to family dinner or something. I luckily have the option to do so as I know I live in a household where I will not be kicked out.

So far with my family I'm pretty sure both of my sisters at least assume that I'm not straight if not gay (I've never been on a date or had a relationship so yeah), and while my dad is not as accepting of LGBTQ people (mainly gay men and transgender women) as much as my sisters I know he'd accept me. My dad's parents are at least tolerant and my mom's mom isn't but I don't want to worry about that too much.

With my mother, on the other hand, I have no idea, or at least my current idea is leaning towards being a bit more negative. She holds some ignorant opinions no matter how much I try to tell her they're ignorant and is a generally stubborn person. She has internalized anti-Latin@ sentiments and watches Fox news, so she's a bit complicated. She talks of being accepting because she "has gay friends at work" but she is really into stereotypes of gay men and I at least know she voted for prop 8 in CA in 2008 as she thought "separate but equal" would actually work. I don't know how she feels about prop 8 nowadays as it is 5 years later since she told me her opinion but I do see her acting squirmish or grossed out when she sees men kissing. We were watching Teen Wolf and she acted weird because Danny and Ethan were holding hands like seriously (my dad thought it was "funny", wtf people)! Every show she likes condemns homophobia so I don't understand how she can be like that. I don't know how she feels about lesbian, bisexual, or pansexual women, all I have are her reactions to male-male relationships. Anyway, I at least know that my mom has assumed if not hoped that I'm straight by certain things she says involving marriage and dating, a recent comment may be the opposite case but I'm not sure. I go with my mom to the grocery store and etc. every time and I'm scared that my future coming out combined with her mulish ways will put a stop to that as she could want to spend less time with me. Unfortunately my mind keeps taking it further and, as I've always worried about my parents divorcing, I'm scared it'll cause my parents to fight about it if my mom can't accept me and I'm scared my dad will leave my mom. While I don't agree with either of my parents most of the time I do love them both and I really don't want my sexuality to strain any relationships within our family. I know it wouldn't be my fault, but I'd still feel like it would be.

This may seem a little weird to worry about but my mom feels okay with us seeing her in her underwear (when she's in her room of course not all over the house) and this has always been normal in my family. I'm worried she'd be one of those people that think they turned me into who I am and that she suddenly couldn't change in front of me anymore bc somehow liking girls = incest. While seeing my mom in her underwear really isn't something necessary in my life the fact that she'd be like this would be hurtful and would put a divide between us....which is sorta odd but you probably know what I mean right? Like something totally normal in the family would change just because she finds something out about me.

I'm just wondering if there's anyone who's been in a similar situation who has any advice or stories, as I am considering coming out as it's frustrating but I'm not sure about it. I'm really hoping she's accepting but I feel like I could have to hide my relationships with anyone who does not identify as a man until I know she is.

Thanks in advance