Java, there's a lot of times that widowed parents will choose to stay alone if they even suspect their adult child doesn't like the person they're seeing. Your mother had enough good judgement to choose your father for a spouse, and to raise you, and no matter what, guess what, you're still the kid and that's the way it is until some neurologist tells you she's suffering from pretty severe dementia

(some people have a tendency to treat their aging parents like they're saggy, truant children with no sense or life experience).
Encourage her to go out, make friends, travel, see someone if she can find someone she likes, get hobbies, take classes. Most importantly, do
everything you can to encourage her to socialize outside the home and family, to stay active! Don't let her become overly reliant on you/your siblings for social interaction. Keeping active, physically and mentally, having a purpose, a reason for being, is what keeps people from disintegrating. Nothing worse than sitting around in your old age waiting for your kids to find some time in their lives to see you for an hour or two, only to rush off back into their life to leave you sitting and waiting for the next visit.