I don't fully understand the emphasis on not owning a smartphone, and I found the comments about not owning one being the thing that is "really driving me nuts" and about the friends mocking her about not having one interesting. Forgive me for being too personal or speculative, but I can't help but wonder if there's some underlying issue over being the only one without a particular high status item.
I mean, I do think the friends are being rude to make fun, and especially the friend who insists on text-chatting despite knowing that's not practical for the OP. But considering the OP already receives (free!) texts on her non-smartphone, the 'not owning a smartphone' issue seems like a red herring. Owning a smartphone may make it slightly easier and faster to reply, but the OP is still perfectly able to read and respond with her current technology.
Personally I wouldn't send an urgent email at night to someone who I knew didn't have a smartphone, because I'd assume they probably wouldn't have their computer on and be checking their email. Sending a message late at night after the recipient has gone to bed, trying to make plans for the next morning, seems like a problem in and of itself regardless of how it's delivered. I don't think the OP needs to have her phone in bed, but checking it in the morning when you know you have a text waiting isn't more work than booting up your computer and logging in to your emails.
I do think in general it's polite to respect people's preferences. But ultimately if you keep your cell phone switched on, hear it beep and know that you've received a message, and just ignore it, I really don't think you can blame that on anyone else.