I'm going to guess that your mother had at least one domineering, oppressive, and/or abusive parent. Usually when someone regularly uses passive-aggressive tactics, like your mom does, it's because one or both of their parents were despotic. She doesn't know how to just talk to whomever it is she's angry with, because she learned as a child to bottle her emotions/needs or else face negative consequences from her parent(s). Maybe I'm way off the mark here re: your mom, but I'm probably not. At any rate, it might be best for you to just wait until she talks to you again. She's 80 years old, and it's unlikely that she will change at this point, but I don't think it's good for you to keep letting her be an a-hole to you.

So I'd probably just send her an e-mail or text or phone message saying that you're ready to talk whenever she is. And then don't contact her again after that. Wait for her to contact you. She will, eventually. And she might also perhaps learn that the silent treatment isn't going to have the effect she craves anymore.

I have kind of a similar situation going on, and it relates to your post. I stopped talking to my mother about six months ago, because I don't want her in my life right now. She and my father were neglectful of their children, and I don't mean to be dramatic but it basically had such a tremendously devastating effect on me that it ruined my life. I'm ignoring her for kind of passive-aggressive reasons (I can't deny that I do want her to feel some measure of the hurt and pain I've dealt with my whole life because of her), but I mostly just genuinely don't want her in my life anymore. When I discussed this with my sister, she basically told me to just bottle my feelings and keep talking to my mom anyway, keep pretending that all is well, because my mother is getting old, and my sister thinks I'll regret breaking contact with her if/when she dies. This relates to your post in that it's important to NOT bottle your feelings and ignore your needs and let yourself be mistreated simply to keep making the person who has hurt you (or is hurting you) happy and content in their little bubble where they can treat people like crap and get away with it.