It is a mistake. This was pressure and pursuit, whether you want to face that or not. If her family wants your guys to R, then trust me, she knows and feels that, and you being there further exacerbated that. You keep talking about "not wanting to strain family relations" and wanting to keep a connection with her family.
When you get D'd (and these kinds of decisions, no matter how you justify them will get you there faster) will mean you have NO connection and relation to these people. Trust me on that. Blood is thicker than water. They will not invite you to things once her decision to D becomes final. You marry a person's family, but you also D from their family.
DBing isn't a balance. It is a set of principles. GAL. 180s. Detachment. You certainly failed on GAL and detachment with this decision to attend a family get-together for HER family. GAL would have been that you were too busy to attend HER family's get-together. And it showed that you are still attached to her and her family.
My guess is she was not pleased with your attendance......no matter WHAT she said during your sitch.
M(53), W(54),D(19) M-23, T-25 Bomb Drop - Dec.23, 2017 Ring and Piecing since March 2018