Friend barely speaking at mealtimes on holiday?

She's probably just tapped out with spending so much time with another person, it can be exhausting needing to be 'on' all the time when you're with other people.

Also, you trying to make plans for the next day and her saying 'we've got all week' may be her way of telling you to chill, not everyone wants to plan every thing, to you it's a conversation starter and a way to plan ahead (I'm the same), but to her it may be that she wants to wake up in the morning and see how she feels before committing to something, holidays are different things to different people.

Maybe suggest a day doing different things to each other? or rather than assume you are doing everything together, say 'I quite like the look of doing this tomorrow, do you fancy coming with me or would you rather have a bit of time to do what you would like instead?'

If she is chatty the rest of the time, then maybe she needs a bit of peace and quiet at meal times.

Have you considered she might be thinking about you "god, she never shuts up and lord knows how but she manages to constantly talk but eat quickly at the same time and is hassling me to finish. I just want some peace to eat"

Not saying she is, but you have a slight mismatch.

Has she got any time alone? She’s probably peopled out.

You're on holiday together? How is she when you're not at meals? Where are you eating?

I hate talking while I eat. I find it really uncomfortable. In a restaurant I have a hard time hearing what other people are saying and I'm overly conscious about food in my mouth.

Could you suggest eating separately and see how that goes down?

Very odd. Maybe she's exhausted by travelling? I know sometimes I find it hard to keep making polite conversation and just want to curl up on the sofa.
Think I'd be tempted to ask her if she has a problem with you if it goes on much longer when the travelling to holiday excuse definitely won't cut it.

If she lives alone she's probably finding it a bit full-on to be with other people all the time. Holidays can be quite intense for this, even if you're not introverted!

Haven’t you answered you own question here? When you meet up from time to time for dinner she is chatty, but on holiday you’re likely eating all of your meals together, so conversation may well run dry as you have nothing to update on another one as you’re together for a chunk of time. She might just need some decompression time, it’s intense spending a lot of time with someone that you don’t ordinarily live with. Can you find a companionable way to spend a meal without needing to talk all the time? The eating slowly thing is another issue and not sure why you mentioned it alongside the talking issue, it sounds like a criticism which I don’t think is very fair.

What is she like the rest of the time?