Some replies and updates from the past few days!
@cubemissy- Yes my boss probably could hear if I called her, but I think the issue was that my boss didn't really care. And not just because she isn't near Tina to hear it, but my boss is typically non-confrontational until absolutely necessary, and they're kind of friendly with each other so there's that. Maybe linked to that is that Tina is clearly her favored/go-to person of the team, so there is a likely chance that as long as Tina was being productive, and I was being productive "enough," then it didn't register on her scale of issues.
@bopper- I considered that method! I was all ready to become a noise scrooge and ask her to keep it down
every time until it got the point across, but that thought is partially what lead me to think this would be an appropriate place to ask first. Because I reversed my train of thought from "Can't they save all this noise for home?!" to "Maybe I'm being entitled and rude for expecting them to conform to my cone of silence..." I also wondered if it might be PA, fighting annoying with annoying or something, if that makes sense.
@VorFemme- Secret Santa would have been the best opportunity! One I'm still considering for another coworker, actually.
Which leads me to a few updates!
There have been a lot of short weeks and days because of holidays which made it easier to look past. Tina has a few humming outbursts every now and then, but nothing close to her singing. I don't like to hear humming either because I'm a stick in the mud, but I don't mind as much since it seems more like habitual behavior than when she would close her eyes, groove around and belt it out when her songs came on.
She did get a little better with the phone calls too...sometimes. There were a lot of days where she would take them somewhere else, or at least keep them short, but it was about equal the days where she'd chat all day. Mostly with her kids though, not the ones where she'd moan and baby talk and mmmmmmm the whole time.... much more bearable IMO. A lot of work friends still visit her desk really frequently, with Not Safe for Lunch subject matter seventy-five percent of the time.
I did get a white noise app for my phone the other day, and thank you thank you for that suggestion because I
LOVE it! It is great for sleeping, and once I got used to having it straight into my ears it was a very relaxing and peaceful day. At first it was hard to get used to, but now it is an enabler because I don't want to turn it off and remember the rest of the world exists

It sufficiently blocks out Tina, and Mr. Constant Bass Leak too. I haven't even had to use max volume!
The important update: Tina turned in her resignation and will be gone in February. She found a new job closer to where she lives and is really excited about it. I'm happy for her- and not just because it benefits me. I do like her as a coworker and a person, just not as a soundtrack.
So thank you everyone for the advice! I promise it didn't go to waste, even though she's leaving soon

Another upside (for my supersonic ears) to her pending departure is that she is much more lax about working and spends
a lot of time away from her desk.