need some advice!

So my boyfriend of 4+ years and I have been talking about getting engaged soon. He already asked my family for my hand in marriage a couple months ago. There is a LOT of tension in my family, mainly between my parents versus my grandma (my dad's mother). It goes way back to so many things. My parents eloped because they didn't want my grandma taking over their wedding. So anyway, my grandma has two diamonds, one for me and one for my brother. She said they were each appraised around $6000. But I'm not sure, I haven't taken it to the jeweler. My parents flipped out when she offered that and thinks my boyfriend should pay for the ring and if he doesn't have the money to get me exactly what I want then we shouldn't get engaged yet. They keep telling me I should make it into a necklace or something so I don't have to look down and my engagement ring everyday and think of my husband AND my grandma. Which I pretty much agree... they said my grandma is not offering me the diamond, she's offering it to my boyfriend. my boyfriend wanted to do it because he wants me to have exactly what I want and have something amazing but knows he can't afford it. He would get the setting and the diamonds around it and all. But now he wants to get it himself. He just wants to do whatever I want. Honestly we didn't even go ring shopping yet so I may like something that he can totally afford. But now my grandma is so mad that we're not going to take the diamond for the ring. I even asked her if I can make it into a necklace and she said no because she thinks I'll pawn it. Then she said fine do whatever you want but now she's telling all her friends about it and saying they are all on her side. By the way, it isn't a family heirloom or anything. It's just a diamond my grandpa got her from zales a while back. It's just upsetting that there has to be so much stress during a time that's supposed to be special for me. No matter what I do it's going to upset someone. What do you guys think? What would you do?