Giving me show cost memo after she receives my resignation letter

Good day!
I got a situation. Due to a big event that is coming in the company that I am the responsible with, I doubt that my boss would allow me to take a leave. So instead of letting her sign a leave form, I talked to her instead and told her that my grandmother is near death and I am asked to be at her side in the province. I assumed that she verbally allowed me because first she never stopped or verbalized that “no you can’t take the leave ” 2nd, she asked me to turn over my work to her and 2 other employees. I also said I am not sure when I’ll be coming back because I cannot predict the situation of my grandmother.
So during my first few days of leave I did reply to their quiries regarding to my work. But after awhile, I wasn’t able to reply to their messages and call due to being busy also my priority that time is to take care of my grandmother and not thinking about my work due to the emotional situation I am dealing with.
Soon as I got back to the office, I submitted a resignation letter because I needed to stay longer in the province. Upon receiving the letter she gave me a show cost memo indicating dismissal.
QUESTIONS:
1. Is it legal or does her giving me a show cost memo after she receives my resignation letter even counts or legit?
2. Am I obliged to do work even I was on leave? Because she’s accusing me that I abandoned my job because I did not reply to their messages though before I left I did turn over my work to her and 2 more employees
3. Can I call this a sever insult? Because now in the office “pinagiinitan na ko” and I am afraid that my remaining days of the 30days extention that I filed might gave her the time to look for ways to make my life more misserable in the office. Knowing that I am in my early 20′s and this is my first job, she can easily manipulate things that could bring to my fall. I am under HR by the way so i think she can alledge me things easily because she's the hr manager.
4. Is it my right to complain because she did not tagged my leave as "with pay" even though i got a verbal aproval from her before taking the leave?
Thank you so much!

you are from HR? is there a policy or procedure that applicationa and approval of leaves should be in writing?

1) yes, she can still give you a memo
2) no, but to answer reasonable questions should be allowed
3) i do not agree this is a severe insult.
4) since they can prove that you were not present, the burden will be on you to prove that your leave was approved.