Echoing others' comments that a) you're amazing b) your English is fantastic.
But adding: twice this year I have been pleasantly surprised by "light friends" who have invited me out for a drink/lunch/movie/whatever. In my over-thinking head, we had to hang out several more times in a group before it would be "OK" and "appropriate" to hang out together and be "friends" instead of "light friends."
But there's no hard and fast rules for that! (like most things in adulthood). If you want to invite an acquaintance over for a beer, go for it! In my case, I was thrilled at the invite and too nervous to make it myself.
Just chiming in from the perspective of older sibling who had to deal with a younger sibling having a surprise child and the whole family freaking out. I spent a long time freaking out (at my significant other) about how TERRIBLE of an idea this was and WHAT WERE THEY THINKING? and Everything is Ruined.
Two years later, it's been bumpy, younger sibling still makes infuriating decisions, and we stress out occasionally about Why Didn't They Use a Condom. But: kid is adorable. Sibling is learning to be a good parent. And my ultimate takeaway? I had so little control over this situation. I kept freaking out and thinking I was going to do x, y and z to "fix it" when I was the last person who could "fix it." So maybe I needed some time to freak out and process my emotions, but in the end, my ranting did nothing.
Once she gets the crying out of her system, the letter writer's girlfriend should figure out realistic, active ways she can be there to support her sister and her parents. They are the ones who will be dealing with the baby (especially if sister is living there). Maybe that will give her some way to move forward, instead of the endless freaking out...because, from my experience, the freaking out feels cathartic and self-righteous but it ultimately really does nothing.