Adults Only! What Would You Do In This Situation?

I just recently had a baby who is going on a month old. I also have a seven year old daughter. The situation goes a little something like this. My "boyfriend" who I just had my daughter by isnt around. I live in an area where everyone knows who comes and goes in my apartment so I actually keep to myself and very seldom have people in and out of my apartment. With this being said the "boyfriend" sister and I have had disagreements and she wasnt talking to me the whole time I was pregnant. Once I had the baby she came to see me in the hospital and wanted to see her "neice".. I let by gones be by gones and I thought she did too.. She came full force for the first week, and I asked her if she wanted to watch the baby so i can do some grocery shopping she said yes then last minute blew me off. She then said she'd watch the baby so i can go do something that i couldnt bring the baby too and then blew me off last minute but then last min texted me and said that she could but i already found someone else. Then she randomly texts me today and asked if my older daughter could go out and play because she is at her friends who lives in the condos in front of me.. I said yes but it was just weird to me that she comes out of no wheres to see if my older daughter who isnt related to her could go and play with her friends kids...to test her i asked her if she wanted to go to my older daughters competition next weekend she told me yes to my face then texts me later n said maybe that she could watch the baby though.. I need advice?