I think the bigger picture here is that not one tiny bit of this is Lisa's business. Whether or not you attended the party, or your reason for doing so, is not her business. Whether or not you RSVP'ed, is not her business. How you do your daycare pickups, is not her business.
I think if you wanted to mention those things in conversation, that's your right, but it is not her place to criticize or tell you what you should do.
Nothing you did here was rude. Nobody is ever obligated by etiquette to attend a party, just because they were invited. If the honoree was hurt, she should take that up with the people she is mad at. If her co-workers, and ex co-workers are not close enough friends for her to have that conversation with, then - hey - I guess that explains why they didn't prioritize the party.
I would suggest coming up with a non-committal stock phrase to respond to Lisa's unsolicited criticism/advice, and just repeat it. I am particularly partial to the phrases, "Really? Huh." and "Well, how about that." They are non-confrontational, meaningless, and make busybodies feel like you heard them, without agreeing with them or committing to further conversation. It is the minimum acknowledgment of "oh, a human being spoke to me."