<human>: Can you condense the text into a few key points?

Let me say first, I love my SO, I can't imagine my life without her. She has been my best friend for 5 years and now my girlfriend for almost a year. I'm going to ask her to marry me soon I've decided. But recently, her sister gave birth (we live with her family to save money) and now she spends almost all the time with the kid. I love the baby as much as anyone but sometimes it's nice for just me and her time. And when we do get that she just wants to sit and be on her phone: she is still in school and I work full time at a customer service center for a internet company AND go to college full time so us time is very rare. More so than usual. So we went on a date last night and I was loving it. Baby was out of our mind and everything. We ended up leaving Annabelle the move because she had to be up at 6 tomorrow and no matter how much of a good movie it was I felt bad keeping her up. We get back and the baby is at her grandparents and the real parents are out partying. Out of nowhere she says we are going to get the baby. I looked at her in disbelief. First night where it was just us and she wanted the kid here. This annoyed her a lot. She thought I was jealous. Not so, I was angry at her due to the fact I just got off a full day's work, helped her with school, dropped $200 with her and all I got was a "thanks" and a small kiss. Am I over reacting? I just want her to myself some nights and she doesn't understand that. It feels like she is putting her sisters kid first, then me.
<bot>: date night ended early, came home and was looking forward to being alone, goes out of her way to be with her sisters baby.