This app was mentioned in 20 comments, with an average of 1.55 upvotes
Tunable is great! For Android: https://play.google.com/store/apps/details?id=com.affinityblue.tunable
For IOS:
https://itunes.apple.com/au/app/tunable-music-practice-tools/id608540795?mt=8
I recommend going into settings and changing the tone generator soundwave to a sawtooth pattern, much easier to hear intonation.
I really like the app Tunable. It has options for just tuning and also other more "exotic" tunings like Kirnberg lll, that work better with the gurdy than the standard equal temperament. If you ever intend to play with others also get a cheap clip-on tuner since it's easier to tune your Instrument with this in loud situations.
Etudes
Since you don't have a teacher use a tuner like tuneable or cleartune and really try to get the needle in the right place. Then get used to what playing in tune is like and what it feels/sounds like.
I don't know anything for the computer, but tunable is available for android too (although apparently now it's $4?)
https://play.google.com/store/apps/details?id=com.affinityblue.tunable&hl=en_US&gl=US
Really, any tuner app will work. Here's one I found that's free (although I haven't tried it as I don't have an android)
https://play.google.com/store/apps/details?id=com.soundcorset.client.android&hl=en_US&gl=US
I guess you have to decide whether you want to improve or if you just want to do fun things. The reality is, most of the best practice isn't the most thrilling stuff on the planet. Surely you can endure 10 minutes of focus once a day. It's really not that bad.
Do it with a tuner. Make a game out of it. I personally like Tunable because you can see a short "history" of your pitch tendency and there's also feedback on how long you've held it in the center.
You could also do Chicowicz air flow studies and just hold out the first and last notes a little longer. Or do lip slurs and hold out some of your pitches a little longer.
I used Tunable for a while, but mostly just for the metronome. I'm a percussionist and never found the tuner very good for timpani. Perhaps it's better for other instruments, but I never tried. That was also back on my Note 2, so maybe the mic wasn't as good. Now I just use an actual tuner.
https://play.google.com/store/apps/details?id=com.affinityblue.tunable
You could always use an app that will give you a pitch and listen to it through headphones (bluetooth earbuds ftw btw). The tuning app Tunable has a pretty good "pitch pipe" functionality that will hold a given straight tone for as long as you want for this purpose in any octave. And I'm sure there are plenty of other apps out there.
However, I'd aim for a more organic approach. Just find the key through a bit of noodling rather than hammering on one key. You're virtually always at most a half step from a note that works in a given key. You can do some very quick noodling and figure out "nope, F# doesn't work" and now you've just eliminated like half of the keys. If you can single out Bb or F#, you can do a very quick process of elimination and find yourself in the key any song is being played in. You can practice this by just playing along with random songs on Youtube or Spotify.
Another good option is to learn the basics of a fret board and maybe some chord shapes. It's totally worth learning basic guitar anyway, but if you have a guitarist playing, often they will play chords that are dead obvious. Most of the open chord shapes are super telltale. There are a handful of very common barre shapes that also give their quality away and then it's just an issue of knowing if the barre's root is on the 5th or 6th string and knowing the names of your notes on those two strings, or at least know how to count up from E or A.
Same idea with an electric bass player, though you really have to watch a little more closely as you might not be able to cheat by looking at a chord shape and actually have to see exactly what they are fretting.
Beyond that, remember to always listen to the bass line to give you an idea of the outline of the chord progression.
Best stand on the market imo. She may think getting a really nice music stand is hella lame but as she gets older she will get angry at those silver travel stands that's literally break after 3 minutes.
I think I also own http://www.sharmusic.com/Accessories/Music-Stands-Accessories/#page_no=7&src=&_=1480946564547 not 100% sure since I am not at home and it has no brand. If it's the one I have it(which I am pretty sure it is) it's really stable and good I use my manhasset stand for when I am playing standing and my travel stand for sitting.
http://www.sharmusic.com/Accessories/Metronomes-Tuners/#page_no=1&fq=ATR_Brand%3aKorg
Is a pretty solid tuner. I also suggest the phone apps Tuneable for tuning and keeping time. I also recommend Intonia for long tones.
I use the android app Tunable. I've been very happy with it, and it has a transposing setting.
I would recommend Tunable since they've different tunings (e.g. Just) that go well for gurdies.
I use tunable and it's pretty good, certainly better than anything else I've found
I use tunable (Android).