They should be able to hold their wee for minimum of 2.5hrs to 3hrs, so you should be able to go out for longer than 30 minutes. We potty trained during the summer, so many chances to be in pants and be outside in the garden. My girl is Sept '21... she just started telling me herself that she needs to go or just went to the potty on her own. Our first trip out was to a comic con and she held it in for way longer than she should have despite me bringing a potty or going to the toilet- she would refuse to drink whilst out for a wee while but eventually started to go to the toilet and has been asking for a drink. Try not to make a big deal out of it, the more you push the more likely she will refuse and it will just cause you problems. Just go to the toilet and ask her if she needs to go and leave it at that. She will get the hang of it.
It sounds like they might not be ready. I tried potty training Freddie at 2 years and 4 months and it was a shit show, he just didn't understand or grasp it and would have accidents in the car on short journeys. I stopped and waited until he turned 3 (3 months and 2 months to be exact) and we are 1 month into it and he's only had 2 accidents and that was on the first and second day. We've been out all day with a travel potty and he'll wait several hours to use it and doesn't need prompting. He also goes 9 hours at nursery and takes himself off to the potty. I genuinely feel like there is a right time for every child x
From what you've said, she's definitely ready 100%. Don't give up. It sounds like she's doing really well. It's only day 7 she will get the hang of it, My advice for longer trips is to take a few spare pairs of clothes plus socks and shoes in case of accidents, make sure she does to the toilet before leaving the house and definitely don't resort back to nappies I know it can be difficult, can you reward her with stickers or have a sticker chart, also I'd get some steps and a toilet seat so she feel independent and like a big girl. I started when mine just turned 2 it took me a while to fully crack it but once I started I didn't give up and didn't resort back to nappies as it just prolongs it and causes confusion. Good luck
Also, know where the toilets are when you go out and any time you pass one try to get her to go. She might still have accidents for a while, potty trained mine in May last year, she could go herself from the start, but she still averages 1 accident a day. You get used to dealing with it and the accidents get much smaller, as they notice they are having one and stop themselves.
They just might not be ready. There's not one set way to potty train, every child is different. With our LG we used pull ups and encouraged her to use the potty when she realised she needed to go. Some say this is confusing but it honestly just worked for her. I suggested wearing knickers a few times, but she wasn't ready. One day she just asked to wear knickers and within a week she was trained. Like a lot of things with her we've realised we can suggest things as much as possible, but until she thinks it's her idea, we probably won't get very far (was the same with getting rid of her dummy). I feel like I could have saved a lot of stress if I'd realised this sooner 😂
Honestly we tried my our little boy at 2 years 6 months old and he started off well and then it all went south. We then tried again, on his terms, at 2 years 10 months and we whizzed through it and he's been fab since, now nearly 3 years 5 months. But I know boys and girls seem to have very different potty training experiences x