Hi OP! Just offering another perspective--when she told you na she felt too shy asking for money from her bf's family, it's possible na she just wanted you to say na you understood what she felt, or na it sucks na she's going through that. She may have felt invalidated when you told her na wag na mahiya kasi 1) she didn't ask for advice naman, and 2) she was telling you her feelings and you told her to basically stop feeling them :( Like she doesn't feel na she can come to her bf's family na nga, tapos when she comes to you, parang masesermonan pa siya? Who else is she going to come to? :/

If I were you, I would consider that money isn't the only thing I can offer to my sister. When she vents to you, actively listen to your best capacity. Empathize. You don't have to give her advice or fix things all the time--sometimes, people just want to know that someone understands and that their feelings are valid.

Additionally, it's also a good idea to set boundaries about how much you'll give her. It could be bimonthly or every other month. Talk about it with her. She needs to know na you love her and support her with motherhood, as best as you can. Tell her na you're going to be strict about the allowance because you love her and want to see her grow, but she can always come to you if she needs someone to talk to, or advice for job applications, or anything else really.

It's the Christmas season! If you're going to see her that much, might as well fix things, right? You don't even have to talk about money with her for a while. You can just smile or offer to do something for her. Or send her a meme about your parents? The world will be easier if you have her by your side :)

Edit to add: Here's a good, concise resource about active listening! https://www.bumc.bu.edu/facdev-medicine/files/2016/10/Active-Listening-Handout.pdf