So this is essentially my "lending" life. I'm the oldest of 7! and hubby has 1 younger brother. Until very recently, all these younger siblings pretty much sucked at money and would find themselves needing loans for various reasons I either agree or didn't agree with. All good people, good kids, not necessarily "spendy" even, they just go along with their lives spending 95-100% of their incomes like everyone has told them.
But I digress. Basically, hubby and I evaluate requests for loans as they come in and what the reason is. And like you, if we support the "cause" and we have the money, then usually we go ahead with it. If they pay it back, fabulous. If not, we never "lend" more than we can afford to consider a gift that we can give without bitterness if it's never repaid. To date, all these loans have been repaid, although there was 1 or 2 that literally came back to us so longer after the original lending date, that we had utterly written it off and forgotten.
I try not to evaluate the siblings other purchases during the same period in either a negative or positive way. Because let's be realistic here, the vast majority of society is telling them they are doing fine. And I'm not here to convert people to 1) conservative frugality, which is what I would say hubby and I were doing before I found MMM or 2) Mustachianism, far superior to even what we did previously. You'd drive yourself crazy doing that because most people don't have the insight that hey if I didn't buy this latte every morning, I wouldn't have ever needed to ask big sis for cash to cover *insert emergency/need here* that my own savings was inadequate for.
Also OP, she may be asking you out to brunch etc as a way to show her gratitude. Because to her spending money to socialize is showing appreciation.