To expect her to be on time!

But wouldn't she just adjust her lateness to the new time?

I totally get where you're coming from minimo , its like she is saying her time is more precious than yours.

I agree with Gaga tell her half an earlier than you plan on being there.

Totally agree with leaving the meeting place after 10 mins. Go for a coffee and when she rings, give her directions to find you.

I'm feeling cross just reading about this!

Just tell her that, from now on, your maximum waiting time is 10 minutes unless she texts/phones you with a VERY good reason for further delay (motorway closure, broken down train, that sort of thing). And, if she's more than 10 minutes late - leave.
Her behaviour is inconsiderate and rude but perhaps she hasn't yet realised just how much it aggravates you because you've laughed it off. She needs a wake up call and, if she really is a good friend, she'll get over it and mend her ways.

The simple answer is to give her a time 30 minutes prior to the one you want then there is a chance you will both arrive about the same time.

It's plain rude.