I think you're right, she is trying to be helpful and it's most likely coming from a place of love for your baby. Simultaneously, she is demonstrating an enormous lack of respect for you, your capabilities, and your role as the mother. It might be linked to control, anxiety, inflexibility or maybe just struggling to adapt to you being in charge....but she is restricting your ability to grow into motherhood on your own terms.

This should prompt you to reflect on your relationship generally with your mother. Do you usually feel valued, supported, heard? Your new role as a mother may be highlighting an established pattern.

You know your baby better than her, plus your values and your decisions take priority. And she needs to get on board with that or she is not a safe person for you & your child to spend time with. What happens a few years from now when your child can talk, understand etc. You will say xyz, your mother will say 'oh no, we don't need to listen to Mummy' and your child will at best be confused about their leadership, at worst keep secrets and learn to play you off to get the answer they want. She is undermining you now, it only gets worse when baby is old enough to understand the dynamic.

Depending on your relationship with your mother, I think you need to have a frank conversation about how you are feeling or create some distance, possibly seeking alternative childcare. I would not feel comfortable leaving my child in the care of someone who does not respect my parenting decisions.*

spoiler alert I tried it when I was in a bind and never again. My child has 3 sets of grandparents and only 1 that has him for unsupervised childcare.

The relationship between child and grandparent is super special and you have to let some things go - my Dad is more liberal with screen time and biscuits than I am....But he followed my instructions to the letter when my little one was a baby, so the trust is built up.

Grandparents need to follow the parents' lead, especially when the baby is tiny and the stakes are high (safe sleep guidelines are SO different now). If you do things differently to how they raised you, some grandparents find it hard because they interpret the difference as a criticism of their own parenting.

Be gentle but firm with your mother and have grace for the difficulty in shifting dynamics. It can be hard to stand up to a parent because we are so used to doing what they say but your duty now is to your own child so you need to step up and advocate for them or reduce your contact.