Before getting braille music, someone may want to ask her if she can read Braille, and if she can read music Braille. Not everyone can read Braille. If she has enough vision that she can read large print, she may not have learned it.

Does she have an iPad? If someone can provide the music to her in an electronic format, she may be able to enlarge it enough to follow for herself. Not as light as paper, but she would have control over how much to magnify and may also adjust the contrast.

I wouldn't assume that she knows Braille, and even if she does know Braille, it's even less likely she knows musical Braille. I would go so far as to say that if she did know musical Braille (highly unlikely), she would already be using it.

To print out Braille, you need a Braille printer, which is also expensive. There are Braille printing services that will send you Braille but they can also cost a decent amount, and Braille can get really bulky really fast.

Here's something that might be practical for a low vision musician who can still kind of see paper. Put the music on an iPad and invert the colors using the accessibility feature. This may or may not help, but for many forms of low vision or partial blindness a screen is a lot easier to read than paper, for whatever reason, and for many others high contrast black backgrounds are also easier to read. Certainly not universal, but worth a try, and it might be something she hasn't yet realized herself yet.

Before doing anything unilateral, it's definitely worth having a conversation with your choirmate! That is pretty much always true in these kinds of situations.

I wouldn't do anything without asking her first. One, you can find out what kind of help she needs. Two, you can find out whether she wants any help or not. I know you're trying to be nice and considerate but there's a possibility she doesn't want/need your help and will only feel patronized if you try to give her something she didn't ask for. It'll save you some awkwardness. :)

I would talk to her to ask her if she needs any help; it’s actually pretty normal for people with visual impairment to hold things that they are reading really close to their face. You could offer to do some cutting and pasting - kind of revamping the music so it only has the soprano or alto part and measure numbers, and spaced further apart, for instance. That would make it less visually cluttered and would probably help her out quite a bit, actually. That’s just my suggestion.

I have a music stand that I attach to a cymbal stand that gets closer to my face. For band I also type out my music so the spacing between the lines of the staves is bigger. It really helps when I’m playing vibes because I can’t read sheet music if it’s farther away than if I was at a piano providing its large enough but for drumming since a lot of it is ostinato I just memorize.

Marry her....