First of all, I'm very sorry, MirrorKnight.
I agree, it's a good idea to fly out Friday night so you won't take too much time off work due to your tight schedules. I would visit your grandma while she's still alive as opposed to attending her funeral. She can hear your voice even though she cannot answer you.
When a loved one was about to pass away, I said to him, "Just go around the corner. I'll be ok and I'll catch up with you." He looked at me with his beautiful blue eyes, couldn't speak to me but he understood my every word. With that, he passed away. It was so hard, so very hard.
Even though it's extremely difficult to say your last good-byes to her, know that both of you provided each other with priceless memories especially when you were a child. You will forever hold a very special, dear place in her heart for all eternity and likewise for you as well. That right there is something you'll always treasure. Look at the positives and cherish what both of you gave each other way back when.
If you're religious, pray and if you believe that her body is just a shell and her spirit will rise, then believe that for comfort. For many people, we believe that life on Earth is just temporary and there is a better place and new life elsewhere.
Oh yes, I've dealt with what feels like hundreds of non-empathetic types thus far in my lifetime! I've discovered those who lack empathy and have low to non-existent emotional intelligence (EQ), were on the receiving end of the same treatment whether it was from poor parenting, toxic, dysfunctional home lives, brokenness, mental and / or physical abuse over the years or decades and feeling overwhelmed by repetitive cruelty.
You can't teach what a person doesn't know. Or, they could've been sweet, naive and innocent once upon a time, they met and married the wrong person, abused to smithereens and if you can't beat 'em, join 'em. Some people were kindhearted long ago and then became tainted and corrupt due to their abusers and wretched environment. I've seen and heard it all and nothing fazes me, MirrorKnight.
I've noticed empathetic people and those who possess high emotional intelligence tend to surround themselves with alike minds. Their family and friends tend to be normal, loving, nurturing, caring, honorable, very moral, decent human beings or so I've noticed. You're a product of your environment and whom you associate with for years.
If all you know is meanness, hate, total disregard for other people's feelings, accustomed to habitual disrespect, deceit, betrayals, lies, manipulative behaviors, gaslighting and the whole lot, you become just like your perpetrators. If you lie with dogs, you wake up with fleas.
Yes, people who lack empathy are unkind. All they think about is themselves and it's all about them. They're incredibly self-centered and selfish.
I've also noticed that people who have insurmountable problems whether it's poor health (or a family member), shaky finances and train wreck personal relationships (3 biggest worries) are very miserable. Therefore, they'll engage in the "misery loves company" tactic on you. They want you to be just as unhappy and insecure as they are so they'll say anything to either make you angry, upset, sad or all 3. It's human nature.
You're not overthinking. People behave oddly and disrespectfully for a reason. It ALWAYS stems from somewhere and not a good place in their mind.
Some people are just indifferent. They don't care and it shows. It should not come as any shock. You'll become wary and jaded. What helps is lowering your expectations of others. If they're kind, then great and if they're not, most of the time it's actually considered the norm on this Earth. Don't put too much stock in people and you'll be happier.