She could heave easily said oh let's sit here witb these guys. And then ignored me if she wanted.
She didn't want to sit with you OP! Or have you at the table making her feel awkward, or have to sit there ignoring you, she'd already ditched you the day before, she didn't want you there with her at all, she didn't ask you for breakfast or invite you to sit with her, you purposely engineered it so you were there at the exact same time as her and assumed you would sit together. IMO It's not mean, petty or rude of her to leave you there, it's just awkward, and it's only awkward because you didn't get the hint from the day before.
The way you are talking about 'bonding' with people kind of makes me think that you thought you would meet someone and automatically pair up with them for the weekend, and thought you'd hit the jackpot with another single parent, it really doesn't work that way at all, and that neediness would make most people feel uncomfortable or stifled or obligated, even if they acted nicely/politely towards you.. they'd be looking for an excuse to get away and you should have accepted that, you can't win them all.
You sound like you needed another adult to go with you to feel comfortable, it's not your fault, especially if you're not very social, but no one else at that event owes you anything just because you are on your own, you've either got to be a social butterfly and mingle, or accept that you may spend quite a bit of time on your own and planned accordingly.