Spurred by the quarantine, girlfriend and I hastily moved in after two months of dating back in June. Around our three-month mark, her 12-year-old niece was subjected to serious trauma from her abusive mother and psychotic sister (professionally diagnosed). Having come from an abusive home, my heart broke in empathy for what this child was going through and so I immediately suggested to my girlfriend that if she wanted to take her niece in until they found psychiatric help for the older sister, I wouldn't be opposed. My girlfriend looked relieved that I brought it up and said she was glad I mentioned it because she wanted to take the niece in but wasn't sure how I'd feel.
Over the course of the next two months - to put a long story as short as I can - I took care of the child. Maybe it was a combination of being the eldest of my siblings contrasted with my girlfriend being the youngest, I did a significant portion of financially contributing to the niece, making sure the girl was fed, taking regular showers, having clean clothes, and although I didn't feel close enough to have serious talks with her, I encouraged my girlfriend to regularly check in with the girl to discuss how she was feeling and to overall just make sure she felt loved. Sadly my girlfriend was neglected as a child so she really doesn't know how to show affection with children (she does great with me and her dog).
When all was said and done, I felt like my girlfriend never acknowledge how much I stepped up and sacrificed during those two months. I can recall a tight hug and a heartfelt, "Thank you for helping take care of her, you're the best" but it felt no more weighty in gratitude than one might express to a lover after they microwaved a cup of soup for them as one lay bedridden with the flu.
I wasn't expecting her to be or feel indebted, but I guess I was expecting some form of acknowledgment that demonstrated she understood how much love I have for her and taking care of her family. I haven't actively stewed on this over the last seven months but I think it subconsciously really bothered me because those two months with her niece randomly came up today when my GF said, "Remember when we took care of my niece for those two months? God that was such a rough time" and I caught myself feeling bitter because I put in 90% of the care for her niece, never said a word, and the acknowledgment I received was displayed in less than 9 seconds. I feel guilty for feeling this way, but I feel like I want to discuss it with her.
How do I approach feeling unappreciated for taking care of my girlfriend's niece for two months?