Your husband needs to learn that you are his first priority, not his Mother. If he wants to pressure you into giving your baby to his Mother, then tell him that you will happily give his Mother her baby back, yes ‘HER BABY’ I would send him to his Mum’s for a day so she can have her baby for a full day and you can be left in peace with your baby!
I would make it clear to both your husband and your MIL, that your tiny baby NEEDS to be with YOU!!! You are their primary carer, they have known your heartbeat, your smell and your voice for the entirety of their existence! It would be completely distressing for both you and your baby to be separated before you are ready! This is where breastfeeding gives you an advantage, as if you breastfeed, your baby has to be with you at all times. It should be no different if your baby is bottle fed, your baby needs you just as much as she would if she were breastfed.
I would go as far as saying ‘MIL, I love you dearly, I look forward to seeing you and baby having a wonderful relationship in the future, however, right now she is a tiny baby and she needs to be with me. I have no intention of giving her to you or my Mother, or anyone else for full days or overnight until both baby and I are ready for it. When that time comes, I will be sure to let you know! You have had a precious newborn yourself, this time is so short and is over so quickly, it is my time with my newborn and I am not ready to be apart from her! Until then you are welcome to visit us, we have invited you over several times, we won’t be going out visiting in the evening, as our baby needs a routine but you are more than welcome to visit us at home.’
If MIL is rude or angry at this, then you can tell her that you don’t need to invite her over at all!