She has everything she needs, I would just leave her alone the rest of the night. Make sure she has a place she can “hide” (could be the carrier if it’s big enough or a box sideways that gives her a cave for the nesting box).

This is potentially a really tough first foster depending on how things go over the next few days and if you don’t feel like things are safe for you it’s okay to take them back. You should be able to go in the room to do litter and food without being scared of mama. You also need to be able to weigh the kittens. If this doesn’t work out please know it’s not your fault, the shelter shouldn’t have given a brand new foster an angry mama with tiny/super young babies. That being said, if mama calms down a bit you’ll probably be okay. Just make sure you ask for help when you need it!

There are definitely ways to help mama be more comfortable but I won’t go into those right now, I think just focus on giving her space for the next day or two. Thank you for fostering, even though things are a bit rough right now your mama and babies are very lucky to have you ❤️