I was a gestational carrier (surrogate) for my best friend but I refuse to do the same for my sister and I lie so my family don't give me shit for it?

I have two kids and last year I was a gestational carrier for my best friend and her spouse when my best friend was unable to carry a baby herself. I volunteered because I love my best friend and I never had any trouble with my pregnancies and I knew she would be an amazing mom. When I was pregnant with my best friend's baby my sister told our family that she had been diagnosed with infertility that made it impossible for her to have biological children. Her attention and the attention of several other family members turned to me since I was already a surrogate. But I have never had a good relationship with my sister and I didn't want that nightmare of navigating the process with her, so I lied and pretended the pregnancy was rough for me. And I have continued to act like I was done after that because of the issues I ran into (there were none really). My best friend doesn't want more than one child so it should never be an issue. But my family have no idea that I could do it for my sister too but I just don't want to.