I'm with you...I think the minimum given that you are taking up a (what could be) a busy lunch table and the fact that despite you did not order lunch your chips were replenished (no obligation there on her part) was $10. To count out $1 per drink...thats laughable.
Even more laughable is the assumption that to be "nice" to her was more desirable that the extra bucks...EL CHEAPOS!!!!!