New and looking for solutions; How do I know when she can no longer (safely) live alone?

Hello everyone. I’m brand new here. Looking for support and commonality. Here is some information about my situation. My mom is 87 this May. She lives alone and is in what I would call fair health. By that, I mean she has no significant chronic issues other than circulation issues and her only medication is a blood thinner and cholesterol medication and an anti-depressant. She is mobile, although she is weak and shaky when she moves around and should probably use a walker, but refuses. I am her only caregiver in that I go by and check on her a few times a week (sometimes taking her food), take her grocery shopping (or do it for her) and take her to her Dr. appointments. She refuses to get out of her apartment for social activities other than coming to my house occasionally when extended family is in. Says she has no desire. She lives in HUD housing for Seniors in our small community and she doesn’t even go to the commons area and visit with the others who live there.
I am beginning to see more and more signs of forgetfulness and confusion in her. I think that part of this is due to her inactivity and lack of motivation. And while I contribute some of this to depression, I know that most of it is just her personality. She has always been a homebody with low self-esteem that shuns social activities. But as I said, that’s always been her personality. Another contributing factor is probably her circulation issues which have resulted in multiple TIAs before getting carotid stents. So there is some actual neurological damage, although the Dr. said it was minimal.
Due to her lack of activity and desire to get out and about, her day consists of sleeping or staying in bed until around 1 pm. (She says it’s because she doesn’t feel well, but honestly she has always been a layabout in the mornings.) She then gets up and moves to her recliner and sits there in her gown for about an hour or so. She will get dressed and fix herself something to eat by 3 or 4 – depending on how she feels that day. And then continue to sit in her chair in front of the TV and doze until bedtime. I believe she goes to bed around midnight. She “watches” TV, but keeps the sound muted because she can’t hear and doesn’t see the point in putting in her hearing aids when she’s home alone. So basically she has no auditory input, no social input, no mental stimulation 90% of the time.
I am quite sure that the lack of mental stimulation is a contributing factor to her decline in memory and processing skills. My husband (and other family) tell me to “make” her get up and do things. But she just doesn’t want to and it makes her angry to try to tell her what to do and I just don’t see the point in fighting with her about it.
So….(after all that) here is my question. How do I know when she can no longer (safely) live alone? Right now, despite her memory issues and confusion, she seems pretty OK. I go over when she showers in case something happens. She is able to take her medication pretty consistently although it was a battle to get her to let me use a pill organizer that I refill for her weekly (“I know how to take my medicine!”). She can cook simple meals and most things I buy for her are microwavable. But I worry that she will forget about something she’s cooking or something like that. She did have a minor grease fire already because she thought the burner was off and it wasn’t . It seems crazy to wait until something terrible happens to change anything. On the other hand she is ridiculously hard headed and I know that she will be horrified by the thought of someone coming in to help her or moving to assisted living (or in with me and my husband). It’s a battle that I don’t want to face until I have to. Am I being irresponsible by not being proactive? I worry about this constantly. I guess my problem seems minor compared to some of you who are right in the middle of 24/7 care but I see it coming and I feel very unprepared.