Just talking and or treating her like a person would probably make her day

please also keep in mind that not everyone wants to get special treatment, as another user says, just treat us like a human being because that's what we are first and foremost. sometimes just going places and being ignored or blending in with the crowd is what people want. granted, that isn't everyone but that's where you would need to be able to read the person's responses and how they're reacting to things.
i'm not saying ignore her, but make sure that she is accepting of the attention before showering her in it, ya know?

Ask, don’t assume. Ask her how you can help best, if she would like some descriptions of what the others are doing or saying, find out from her. Every person is different, and has different preferences (plus, every blind person has different amounts of useable vision; she may not be totally blind, and have enough vision to get a sense of what the people around her are doing, for example). I appreciate the sighted people who want to help me, but appreciate just as much when they listen and leave me be if I say I’m good. It’s really important to find out what that particular person wants or finds useful, and go from there.

Maybe offer to get her some new needles / hooks for her crocheting? Or maybe find some bulk yarn to give to her! A lot of thrift stores will have yarn in loads laying around.

As for the second part, I’d say ask her what she prefers. I know that I don’t normally care all that much when I’m attending service but that could be different for her. :> hope this helps!

I did this long time ago when I was younger with a neighbor. Ask them what they look to cook or eat... If they say "well you know..." make a dinner date with them. You'd be surprised how much warmth someone gets from someone who cares enough to fill them up. Food is the best entrance to someone's life no matter who they are.

if you're interested in hanging out with her a little and she seems open to it, you could ask her to teach you crochet or other skills she uses - not to generalize but most older ladies i know would love to pass their skills on to people who are interested, and spending time together learning could help you get to know her better so you'll have a more accurate idea of what other kinds of gestures might be meaningful to her. of course, not everyone is up for teaching and that's understandable, but generally it doesn't hurt to ask and it's something you know for sure you can talk with her about :)

Wow, what an amazing question! I know I'm a little different as I've been blind my whole life, but I can't imagine how difficult it must be for someone who lost their vision later in life. For me, all I want to do is get to know people, but more times than not, they're nervous to approach me, either because they're afraid approaching me would be rude or I would be rude to them which I sincerely hope never happens. Honestly, treat her how you would want to be treated in that scenario.

So G. Carlin was right! People go to church to compare clothing :O