She either sent them a really obviously begging DM saying, hi guys do you have any tables/vegan options? And they said, yes we'd love to have you one night for a post and some stories (she'll just do the stories).
Or they got in touch with her and offered a visit. Friend of mine who is a food instagrammer has had hundreds of visit/gifted offers recently as they try and claw back everything they lost over the lockdown, he'll go and post the photos/stories however he always makes a point of paying or least paying 50%. It's all about PR for the restaurant, I mean it's worked, we're all talking about Giggling Squid now, although with her maybe less likely to go now
I get the thought of passing it on to NHS worker or similar but then the restaurant doesn't get much Instagram reach sadly.
At the end of the meal she'll ask if there is anything to pay, the waiter/waitress will say no all good. BUT it is always standard for a gifted meal to still leave a tip, you MUST leave a tip which goes to all the staff! I've been with my friend before and when we've realised we've forgotten the cash one of us will run out and get some.
God I hope they've left a tip to their waiter on minimum wage.