Ethical dilemma

I had the most upsetting experience at a party in Soho this evening. I had been invited by X, a new friend whom I like very, very much, to the private birthday party of an elderly family friend, and was touched to be asked. It was a studio party, with a buffet in the corner, and guests coming and going all evening.

On my way home out of the studio door a woman, to whom I had been introduced in passing earlier, called out after me, pointing forcefully to a pot with money, in which she was collecting tithes for a birthday present. I gracefully said that I wasn’t able to contribute this time, and she asked me forcefully if I was a friend of X. Upon replying yes, she said that X needed to remember who had helped her in the past.

Failing to understand what this had to do with my personal circumstances, and quite surprised that anyone would chase an unknown guest for money, I went back up and said that I was so sorry. It was nothing to do with X, that I had recently left my job and that if I gave money I wouldn't be eating next week - (which is the sum of it – every single cent I have is accounted for until I get paid by my creditors.)

Her response was to tell me never to come back there again. I left and burst into tears outside - it was so humiliating.

I later found out that the woman was the wife of the family friend and she must have thought me rude for walking past her & her gaggle of friends in the foyer and not saying thank you or goodnight, but I had no idea that was who she was or, of course, I would have done.

Here’s the thing: should I have given something? I can only go by my own experience: I've thrown many lavish catered birthday parties for myself and maybe a third of the guests at most, the ones I know well, have bought presents. Should giving be obligatory by every attendee at a birthday party?

If I was in full time employment, I would have put ten or fifteen dollars into the pot without even thinking about it, just to be polite, even though I’m not sure I’m comfortable with being commanded to donate to a stranger’s birthday present. Should I have repaid the host’s hospitality by donating to his present fund (which he didn't know about, I hasten to add) even if it left me unable to buy my own groceries for the week?