To think friend should have reminded me?

Its simple. apologise and pay her back, bit by bit if you can't do it all at once. Do the right thing.

If you can’t afford to send her £200 you should never have let her buy the tickets in the first place?

Couldn’t you do a pay later on your banking app? Mine has a pay later on it.
Or set a reminder (5) on your phone?
I hope she went with a friend and had a brilliant time.

15 year friendship seems very much over.

She hung in there for 15 years, hoping you'd learnt to behave like a responsible adult? I only hope she sold your ticket for a profit.

I think You still need to pay the £200.
If you can't afford all of it pay what you can until it's paid off. Dont forget this time.

Phew....I'm so glad I don't have 'friends' like you.

Were the tickets £200 each though?

this

I’ve messaged her now. Apparently she went on her own, she didn’t remind me as she thought I’d do the right thing and then gave up.

There’s more to it than that but I’m not going to post the entire message. 15 year friendship seems very much over. I can’t afford to send her £200.

So what happened to the money you promised from the next payday, or the one after that , or.... You have a conveniently poor memory and chose to prioritise yourself over the friendship.

I don't think she should have had to remind you OP, it sounds like she's not heard from you, not received the money so she's decided to take someone else. If I'd paid £200 for a ticket for someone and they hadn't paid me, I would definitely be chasing them for the money unless I'd found someone else to buy it.

A £200 event gets written in my diary. In red. Circled and underlined.
And put in my phone.
You never had the money to pay so you hid.
You are no friend.

you’re acting a bit like pond scum op. Pay your friend back, sounds like you never had any intention to pay her and wanted a free ride.

shes well rid of you I’d say.

So you agreed to a purchase/loan of £200. The ticket was bought. Now you have recalled the debt you have now decided you can’t afford it. You have also decided not to make any effort to have the other person repaid. Is that correct?

Memory lapses happen, it’s how we respond to them which shows our character.

I wish your ex-friend well as you have shown her no respect and given her good reason not to trust you.

Absolutely shitty behaviour on your part op and you need to grow up. I wouldn’t be friends with you either in this scenario. You absolutely need to pay her £200.

i don't think she should have to remind you but then I wonder if she's lost out if she's gone alone so it might have been better for her to remind you

but also wondering why you didn't know when the gig was

You don't deserve your friend. Glad she ghosted you. I'd have definitely treated a friend who pays £200 for my ticket better.

Were you incredibly busy or something to make you forget something so important? That is usually my excuse.

Sometimes there are threads where someone doesn’t know why one or more friends has ghosted them and ‘why they don’t have any friends anymore’. Pretty clear in this case. Sounded like the dinner invite was the last chance. Did you just say no, or suggest something else? Also another person who can no way understand planning an expensive event and then completely forgetting about it.

You both sound really bloody odd. £200 for tickets, one forgetting about it and one refusing to mention it to the other out of some weird principle. Who does that?

I don’t get why she didn’t ask you whether you still wanted the ticket? Unless you have form for this kind of thing and she couldn’t be arsed to keep chasing you. When you said you couldn’t make dinner did you not suggest another date?

Sounds like you regretted saying yes so you conveniently forgot to avoid paying the money - leaving your friend out of pocket.

I can't see how your friend has done anything wrong here. She subbed you, so it was on you to remember to repay her. I think it was actually very polite and kind of her not to chase and leave the ball in your court. She probably thought when you didn't get in touch you couldn't afford it. Poor woman has now paid £400 to go to a gig on her own because she was kind and considerate to you. Her only 'crime' here was to be too polite snd unassertive for her own good.
If this friendship is over, you're the loser here. So in your shoes I'd be contacting her and offering to pay for the wasted ticket she bought on your behalf.

It might be tricky finding another friend with a spare £200 for a concert they hadn't initially intended on going to.

Sounds like she went with someone else. I’d just move on.

you could have paid for the ticket and she’d still have ignored you.

You know there’s this thing called a calendar that you can write important dates in, you know so
you don’t forget them! Most phones also have a reminder app that you can put things like needing to pay for tickets in so you don’t forget to pay for them. Your friend is not your PA or your mother, it is not her job to remind you.

Pay her the money back, you never know you might even be able to salvage your friendship if you do.

I'd like some of what @Frogpole is on - at least once in my life just for the experience 😅