Advice: Find a singer/songwriter recording on YouTube where you like their sound. Copy their setup.
Start with OurVinyl Sessions if you're not sure where to start. They make tapes in many 'like a home' locations (including outside) and run a variety of mics on solo voice/guitar.
For example, I think this tape of Tyler Childers is a better recording than pretty much any of his other (many) recordings, and he works with the best:
https://www.youtube.com/watch?v=_QzcrflqDCg
That tape is just an SM7B on voice, a stereo (2-channel) XY mic on guitar a few inches above maybe the 8th fret (?), and he's plugged in so assume guitar gets an input too (total of 4 inputs). Can be replicated with a very cheap setup. Just watch out for fake SM7B's, as most on Ebay used are fake Alibaba.com copies that don't sound great.
That's exactly the sound I'm hoping to get (and the 4 input setup I am envisioning), it won't necessarily be the quality you can get at a high end studio, but definitely good enough for distributing if she wants to, and it won't cost her anything but her time. Thanks for the link, makes it easier to visualize what I'm going for.
Nice. As you know, pay a lot of attention to the exact setup locations, which probably matter more than the mics (although in this case SM7B does have a pretty unique sound). Usually, singers are told to eat the SM7B and get super close. For some reason, Tyler doesn't do that in this video. And it sounds amazing.
Same with the XY mic on his guitar. Not sure how much of that they put in the mix, but it's pretty high up and also close to the guitar opening.
So, unusual mic placements that would usually be recommended against, yet killer sound (in my opinion). Also, it looks to me like they're in a big untreated wooden room, with some treatment visible (panels and stuff), and a bunch of rugs on the floor to try and kill the floor reflections.
Room is going to matter a ton (more than mics, probably less than mic setup distances). Have a nice big living room, or a friend who does, or a buddy with stage access?