Newborn cold ??

She woke up for her next feeding and was extremely congested she was always “eating” something in her mouth..? Phlegm? I used saline drops and a suction & she sounds much better now. I’m nervous because the other day i went to my moms house and my younger sister was sick as i thought and my mom kept saying she wasn’t.. one side of my sisters eyes was watering and that one side of her nose was runny. My mom texts me today and says my little sister ended up getting sick.. i know before you even know you have a cold you’re contagious so now I’m worried my newborns gonna get sick.. if i took her temp what would be a worrisome low temp and a worrisome high temp? What should i be looking out for?? Do you think my baby will get sick due to my sister being contagious and her touching the baby’s face and hands?? I’m so annoyed & wish i trusted my instincts instead of listening to my mom.. also i got the flu shot while i was pregnant would baby be protected too??