My (24M) girlfriend (24F) of 7 years have broken up with me since her parents won’t accept the marriage anymore. How would you handle this? What is right to feel?

Firstly, I'm an agnostic, I'm not here to attack any religion just seeking alternative perspectives and opinions on this matter.
So we have been dating for about 7 years, with her and her parents both knowing at the very start that I don't date for fun and do intend to marry their daughter down the line.
Years gone by and her parents and I have gotten on really really well, no problem what so ever. Then suddenly I learnt from my SO that they won't acknowledge my mother as MIL due to some misunderstandings and warned her that I was lacking Christian values. Because of that, I guessed I felt attacked and defensive of my mother, so I started to be less chatty and distant towards them. Unfortunately, they took it as disrespectful and offensive, which led to even more misunderstanding and exaggerations.
After our vacation, they had a sit down with GF in which they brought up 2 Corinthians 6:14 and other verses and they expressed that now they will not accept the marriage. When questioned about why it took 7 years, the answer was they thought that I would turn Christian but now they have realised that I won't ever be one.
A couple weeks went by, my now ex asked if we were to get back how would our children be raised. Just for fun I answered under the condition that it doesn't affect the decision of her coming back or not( I know it did anw). I would like my children to be raised without any influences of any faith but I am more than happy for them if they wish to follow one on their own freewill. To which she later admitted that my answer did affect the decision.
I have a brief understanding of the verse and that I am ultimately undeniably an unbeliever. I have tried to look into the meaning and context through scholarly sources and have given up and understood that it is all just in her hands and what is true to her. I understand that her parents are just looking out for her but still I can't help but feel a certain type of way about how they went about it, almost like it was retaliation and just dealt me an ultimatum instead.
If you are so kind to provide your perspectives and any advice is appreciated.
TLDR: Eventho SO and her family knew I wanted to marry from the start, they now said they won't accept the marriage after 7 years of dating and we now have broken up.