Voicing my concerns about my great grandsons fiancee without offending anyone?

You certainly DO have every rite to voice your concerns! They are living in YOUR home! I cannot blame you for the way you feel when you're there seeing everything that goes on - OR doesn't go on. You've mentioned it your great grandson but he doesn't want to "hurt her feelings"?!?! She taking advantage of ALL of you! By allowing her to get away with all she not doing is doing nothing but "condoning" her lack of actions. Also, possibly if she did something useful she just may loose some of that weight! Please don't be afraid of saying something, again, you DO have every rite to speak up & say how you feel. I'd have another talk with your g.g.son. Tell him it's really bothering you. You can either give him the option of saying something, OR you could possibly mention having a family "get together" & you all can do whatever talking you want. You could easily let them know you DO appreciate their company, appreciate his LONG hrs. he's working, BUT, you really do wish she would do a bit around the house when you need some assistance & want to be able to feel free to ask for it when you need to. By all rites, she should be doing the cleaning, wash, cooking & ALL the things we females do around any "normal" home. You don't mean in any way to hurt anyone, but this IS bothering you & you felt it was your rite to say something about it. IF he marries her, she's going to be one terrible wife! You honestly would be doing him one great favor when you think about it. You are so kind to open your home to them, the least they/she can do is show a bit of gratefulness for what YOU are doing for both of them. Don't be afraid, you should say just how you feel, again, I feel you would be doing them both one big favor!!!...the best to you...:)