Do you respond to every cry? How long do you wait?

My baby is 7 weeks. When my baby cries, I pause mid bite, mid everything or get up almost immediately or within 3 minutes. My mil said I will spoil my baby and my body won’t be able to take it one day soon. Letting him cry will make his lungs stronger. If I stress out too much, her son will stress out too. I started to dislike her because of what she told me. His lungs won’t be stronger from crying. My baby is a newborn. He doesn’t cry for attention. He cries for a reason. She’s right that doing this made me very tired physically and mentally. Should i not respond to my baby so quickly every time? Hearing him cry breaks my heart.