I don't love my grandchild

I really thought I didn't love my eldest GD she always been manipulative from very young and put my DD and the family through hell when she hit her teens but since she grew up (she's 22 now) she has grown into a lovely girl (will always be a drama queen) but she's turned into a super Mum and daughter now and I realised it was her behaviour that made me doubt I loved her.
I agree with all the good advice above keep 'schtumm' and she will more than likely become more likeable at some stage. Remember you are not alone

It's hard to feel much for anyone whose behaviour is awful but it's harder to accept when it's someone you are meant to love wholeheartedly and without condition. I suspect it's something we've all experienced as parents and grandparents, perhaps for just a short while, after a tantrum or whatever. By raising the issue I'm sure you'll discover many of us put our hands up and say 'me too'...

?? me too!

Zip the lip! - not a word to either parent or you will reap some unfortunate rewards.

My DGD of roughly the same age was an angel until a sibling appeared and now we have the attention-seeking, silly voices, demanding behaviour etc. But we just go with the flow and try and help her through it when we have her on her own, and close our ears when she is with Mum and Dad whose negotiations are the current style.

I do not in the least love some of her behaviour, but I do love her. She is just a new scrap of humanity who is finding her way in the world.

But I too heave a sigh of relief sometimes when she goes home - that does not mean I do not love her.

I have said on more than one occasion to my older GD, I love you but I don't like you just now. It seems to work for us but she was probably 13/14 and feeling her feet. We have a lovely relationship now but to get back to the OP I loved her unconditionally from when she was born which sounds somewhat different.

I'm disliking her more and more
That is the sentence from your post that is shouting out to me nannymarg.
You don't dislike the child, you dislike the behaviour.
Get that into your head for starters.
Secondly, of course you don't feel the same way about a grandchild as you do about your own children. She is not yours, she is your DS and DiL's. If you expect to have the same relationship you will be setting yourself up for disappointment.
And whatever you do, don't criticise your DGD's behaviour to anyone, least of all to your DS or DiL.

There are no rules about loving your grandchildren and you should not feel bad about it. As for offering suggestions I would hold back unless parents raise the issue. Maybe she could spend a weekend with you on her own and that time may show you a differnet and more loveable child?

I do love all four of mine but my eldest DGD, whom I love to pieces, has some behaviour that is difficult to like and whist her parents do not tolerate it the poor behaviour continues. I often wonder if she may have a specific problem.

We all love our children/grandchildren in different ways. From what you say it seems that you love your gc but dislike her current behaviour. And that will change /improve as she grows up.