Hey mamas, I have a question. I exclusively breastfeed my daughter so when I’m at work I pump but I…

Hey mamas, I have a question. I exclusively breastfeed my daughter so when I’m at work I pump but I only pump enough for her to eat at daycare. Her dads side of the family, his mom more specifically, wants to take her over night or for a full day. I don’t mind her taking my daughter while I’m at work but I don’t want her to take her for a full day or over night because I don’t have enough milk for her to be away from me for so long. Is it a selfish of me to not let her give her formula if she’s still hungry later or to only slow her to take her at the times that I’m working?