I had the same thing happen
I posted about this on christmas eve after a discussion with my sister. She had the SAME responses.
Although, she isn't cheating on anyone b/c she isn't dating anyone ... and she found out b/c I told her.
She feels that Ouroboros is putting me thru this and that I should find someone more successful, special, whatever. I thought about this for a couple of days, really pissed off and then realized that we view everything differently in life, so of course we'd view success and relationships differently too. Then I was able to let it go.
But, I understand how it is hurtful when someone responds to something you've thought long and hard about and truly believe in in a negative way, especially someone who you love and respect.