AIBU to think this is pathetic?

No, you are not BU.
However, we have been out with friends several times and split the bill quite happily, but recently they have brought a plus one on a few occasions - and we are expected to split the bill without any contribution from the extra person (who is not hard up by any means).

Yes, it is a case if judging who you are with. Normally we are happy to split the bill but occasionally we have been caught out paying far over the odds for what we have actually had.
Last week we went for drinks at a local pub wit some other couples . There was a kitty and each couple ended up putting in around £45. This meant I ended up paying that much for a gin and tonic, 2 cokes and a coffee !

When I go out with friends we always try to have "the discussion" beforehand to save embarassment. But £1.50?!
Next time you are with this person just say I will be paying for myself in a pointed way!

£1.50 is a silly amount to be so petty about.

On the other hand, I recently went out in a group of 8 and some of us drank considerably more than the rest of us , who either didn’t drink, or were driving.
We offered to pay more to cover the cost of the drinks, this was agreed and we all had a very pleasant evening.

It really is difficult especially with larger groups. I was once left having to pay a £70 excess on top of my share due to a couple ordering the most expensive wines, not sharing them, estimating how much they should pay and leaving early.
I couldn't put that on to the others as they were very considerably worse off than the inconsiderate twosome.

I think you should have discussed this in advance to save embarrassment. I have sometimes felt awkward about ordering if l don't know how we are going to split the biĺl.
I have also been annoyed when it ends up far more expensive due to others drinking alcohol.
I love when I don't see the bill and someone else pays.
As you say OP, maybe this is why she is better off.

It was pathetic in this case as it was such a small amount but maybe it is something she always does. I only pay for my self when out with a group as I do not drink and I have friends that like expensive drinks with a meal and I am not part of a couple, there are 3 couples and me and when the bill is split 4 ways I could easily be asked for £75,the cost of a couples meal and drinks,when mine would have been about £25.

Yes, cherry that is pathetic I agree.

As I have to drive home along dark country lanes I don't drink alcohol at all when out for a meal. I always suggest we split the bill but my friends (who do drink) insist on splitting only the food element and paying for the drinks themselves.

Most of my friends I go out with opt to pay for themselves but splitting the bill wouldn’t bother me either, unless one person had loads more Lot of places we eat at you just go to the till and pay your bit yourself
I did go out once to an ‘extended family plus their friends’ do and they split the bill which was grossly unfair as they d had loads of alcohol and much more expensive dishes than us we only had water (by choice I don’t mean we were given bread and water) ?

Ridiculous. As for tips, if I think people haven't contributed, I just put in more myself. I can't be bothered to discuss it.

Some people are just like that (it is pathetic though).

My best story about a similar scenario was us out to dinner with our teenage children (our son was dating their daughter) and when it came to paying, they said "Let's split the bill" - and then pulled out a 50% discount voucher for the restaurant, which was to be applied to their half of the bill!

Cool or what!

Don't go out with her again! I never socialise with people who do that, it just isn't friendly. If eating out with others I always make a point of not having anything which is particularly expensive but, apart from that I just have what I like and split the bill.

The thing I find most difficult is the tip, how to split that? We all have different ideas of how much to tip so I usually end up putting more in than others. Wish it was like Japan where no one expects to be tipped and the service is excellent.

I hate when that happens. Asking for separate bills before ordering is the way to go, if the restaurant accepts this.