GD is behind in her speech

She never stops talking.
She has a wide vocabulary and is perhaps trying to say too much too fast and it comes out garbled.
As she interacts more with other children she may slow up and articulate better.

Has she been checked to see if she is tongue tied? If so, it's a simple procedure to correct it.

For instance since birth she has had a soft bunny called Flopsy. No matter how many times we tell her, she has always said Wopwee.

Sorry, but Flopsy is your name for bunny. Her name for bunny is Wopwee and Wopwee she will probably be for ever.

I remember DGD at about that age telling everyone where she was born and getting the consonants mixed up but she was absolutely insistent she was right.
She would probably laugh if we reminded her of that now, just a few years later.

My DD at age 3 health visitor check was referred to speech therapy. She needed me as a translator, even her Dad had difficulty understanding her.
She had weekly speech therapy which lasted until the end of her first full term at school.
It may be a good idea for your daughter to speak to her health visitor, and get a referral to speech therapy sooner rather than later as the service is stretched at present.

My two younger grandsons are having speech therapy at present, and there are only about 6 of them to cover all of Northumberland. The boys have complex speech problems which should have been addressed much earlier, but they were living in Argyll and Bute where the service is even more stretched.

Measures will be taken if needed

You already brought it up with your daughter and she told you where she stands.

I wouldn't repeat it again.
When she goes to school, she will be evaluated and measures will be taken.

My daughter is the same age and the amount of progress in 6 months is incredible - like night and day
She is bilingual too so it obviously plays a huge role too.

This reminds me of my nephew, getting on for 50 years ago. He would chatter away, but only his mum, my sister, could understand him. We pointed out it was difficult to make out what he was saying, but she couldn’t see a problem. When he started school, they suggested he see a speech therapist, which he did, and the speech issue was resolved.

Not sure how things are nowadays, but feel sure it will be resolved in the fullness of time.

I think we're going to see a lot more of this shortly, to be honest. What you have to bear in mind that your GD has spent two years of her little life not having the same social interactions as toddlers normally would at that age. I come into contact with a good few early years professionals through work now, and they are all saying the same. Young children around that age have missed out on such a lot because of the pandemic - and even mask-wearing is bound to have a knock-on effect too, because they cannot see facial expressions, how the mouth looks when sounding certain words and so on. I'm sure the school will pick up on it if they see it as a problem though. Try not to worry too much.

Could be worth asking your daughter if she thinks it would be helpful for her DD to see a speech therapist?

Health visitors can refer, they might have picked up on the speech delay if your DD booked the appts (I know some parents who hate the HV and don’t set them up).

My child is only 18 months but delayed on speech. Speech therapists won’t see them until 2+