I wonder how many people on this thread have been backpacking compared to having been on holiday?
£180 at 18 when you've saved up, is a huge amount.
Personally I think it a waste because I think about the 'adventure experiences' I didn't do whilst backpacking. I remember trying to do as many things as possible for free and then thinking carefully about the occassional things I'd splurge on. Things like the opportunity to go white water rafting or climb sydney harbour bridge. Things you'll remember for a life time. Or even something you want to spend money on, when you've had a few really shit days - like a nice night of privacy with a bath in a hotel, when you've been in dorms for weeks. Unlike that time you wanted a bit of extra leg room for a few hours at the start of your trip when your still on the high of going at all.
£180 to me represents a whole pile of magical adventures, (that I perhaps wouldn't want to do now I'm older) that you've perhaps only got one opportunity to do. Or frankly, just better spends.
Business class, is a status symbol to a lot of people much more than something you'd put on a bucket list. If I'm honest I don't have a lot of time for people who make a big deal out of how they travelled in a 'better class'. Meh. If you can afford it, and want to do it, fair enough just do it and enjoy it. No big deal. If you can't, then no big deal either. Ultimately the purpose of a flight, is simply to get you to a destination where you then do things. There's so many things, I'd put on a list of things I'd like to do above going business class, so I just don't get it.
Thats why I'd have alarm bells going off. If your daughter is going with someone with that much disposal income and a level of reality that your daughter doesn't have they are going to hit a problem at some point. The tone for the whole trip is set by this.
If they are going for more than a few weeks, it'll go one of two ways;
Your daughter will either run out of money pretty damn quickly. Her 'thriftiness' in getting an upgrade (she didn't need and actually by her own admission, didn't want) isn't a bargin. Its £180 she didn't plan to spend but effectively got emotionally blackmailed / had her arm twisted into spending.
or
Her and her friend will have a massive falling out at some point and maybe even they'll end up splitting up. You'd be surprised at the number of solid / inseparable couples or best friends don't spend their whole trip together and go their separate ways as they meet other people along the way. In some cases, differences are inreconcilable.
In this case, the parents having paid for the rest of the business class ticket, it throws an additional spanner in the works, if they do have a big bust up - it's something to hold against your daughter and a means to which to emotionally blackmail her later on by making your daughter feel obliged to have the trip her friend wants (and can afford) rather than the one she wants and is in her budget.
It really depends on the length of the trip they have planned tbh, but I certainly wouldn't be shouting about how great it was, that your daughter has somehow 'blagged' a really cheap upgrade. She hasn't. I'll say it again - your daughter bought something she didn't want to after some high pressure sales and a bit of duress. Thats not a bargin.
I strongly suspect she's saving up a few problems for the trip itself as a direct result.
You should make the point about making sure she has HER trip not just riding on the tails of the experience her friend wants. Your daughter will enjoy one a lot more than the other.
I genuinely hope I'm wrong and your daughter has a fantastic time but I think you should be a little more wary and offer a bit of caution about how its starting out.