My sister in law makes everything a competition: Help!

I need fresh eyes and opinions when it comes to this situation so I can move forward realistically in this situation. A back story my husband and I have been together 13 years, we have two kids together 12 and 3. My relationship with my in-laws has always been filled with ups and downs because they have a problem respecting boundaries and Metal way too much in our lives, they have helped us financially from time to time throughout the years we always make sure to pay them back. My husband is the oldest first to be married and has kids. he has two brothers and one sister Up until 5 years ago when his sister had her first, she and I were pregnant together and gave birth 4 weeks apart, both girls. it was horrible heartbreaking and disappointing. I was all excited but she turned everything into the competition when I found out I was pregnant she said I stole her thunder, she wasn’t going to find out the gender of her baby but because I did she found out hers, she wasn’t going to have a baby shower but because I said I was having one she had one and my in-laws paid for part of it I didn’t get to have a baby shower cause she threw a fit. After all, the family wouldn’t come to both, when she had the baby she said she didn’t want people at the hospital and didn’t want people to see the baby until the baby had its shots but she had people there just not me or her brother. after I allowed everyone to be there for the birth of my kids. She said she wasn’t throwing her baby a 1st birthday party, after I had my baby’s 1st birthday party planned she asked if she could join our party last min the party cost $800 and they paid $200 this is after babysitting for her for $50 a month and giving her all my baby’s hand me downs that are all in very good condition. she still hasn’t had to buy her child any clothes because of me giving her the clothes my child grows out of and it’s gone to the point where she relies on it and expects it from me. They also took over my daughter’s 2years old party without talking to me or dad first. they didn’t ask if we could have a party for both girls I just showed up with presents for both girls sing happy birthday to both when the party was at my house my husband and I paid for our daughter’s party. She is pregnant again she isn’t planning on anyone seeing the baby again I don’t see my, my niece, much since I don’t babysit. She, her husband, and I recently got into it because they took it upon themselves to discipline yell at my oldest who they made feel bad then told her to keep what had happened from me and I feel they owe an apology to my daughter for how they made her feel and for making her feel like she has to lie to me and her dad but they refused. I got told we are not entitled to time with their kids or to see them, they are not making time for our kids, and that we won’t find out anything unless they want us too. I am angry that they are so selfish and entitled when I am not at all like that with anything, I think they are horrible parents I don’t think they should have any more kids because they are really selfish people and self-absorbed How would you handle this? Oh, and when I need my kids watched by my in-laws there are rules planning, and stipulations but my sin law can just drop my niece off with no warning. I am really angry that my child got hurt in all of this and they refuse to apologize, I am heartbroken that I got attached to my niece and I don’t get to see her or know anything about her often. I am I’m so hurt and disgusted that I don’t know how to handle this effectively. I need advice please.