yes, this is normal. my daughter went through the same thing.I'm not sure if it's for the same reasons - your daughter has just gotten her world rocked by getting a new baby. is the baby sleeping with you or in your room? I think it can feel weird for the older sib if everyone is in one room but them. also, it is normal for them to regress.
in my daugter's case, she had a really scary dream in her bed, which is at the foot of our bed in our room. i was there so i saw/heard how scared she was, and then she did not want to sleep in her bed for a while. she didn't even want to sleep in the room. she wanted to sleep in a different room with one of us. i think their imaginations are starting to kick in, and to them everything is real. they can't distinquish between real and not real. also, this is a big time of individuating from mom, so they can feel very vulnerable and threatened now that she is just starting to realize that you and she are not a package deal. sometimes she's just a little old me. that can be scary, especially alone at night. it is a phase (i have a five year old too).
you can try putting her bed at the foot of your bed on the floor for a while. when she seems steadier, you can move it back into her room eventually. you may all get more sleep that way. when you put her to bed, you can say things like, you're in your safe house, in your cozy bed, mommy, daddy, baby's name, pets names, are all right here with you, etc. mommy and daddy are right up in the big bed, and when she wakes up in the night, just say, i'm here, shhh shhh back to sleep now. and then eventually, you can move her in her room and say, mommy and daddy are right in the next room. if that doesn't work, i would let her come into your bed for a while, then to the mattress on the floor, then back to her room. you'll know when she's ready.
the nay sayers will say, don't let her in your bed, she'll never leave, etc. that's just not true in my experience. my son slept with us since birth and now sleeps like a rock in his own bed all night. i saw a post that said something about not letting her in your bed because you are creating a dependence. news flash: BABIES/TODDLERS ARE DEPENDENT on their parents, that's the way it is. some babies sleep independently with little or no crying. some babies/toddlers/preschoolers have a strong need to sleep with someone else. every dynamic is different. each family has to figure out what works for them. one of my favorite sayings is, a need that is filled will go away, a need that isn't won't. So many of my sleep training family and friends have kids in bed with them, as soon as they can get out of that crib! i digress....
if she is verbal, you could try asking her why she doesn't want to sleep in her bed, did she have a scary dream?, etc. is there something that would make it more comfortable for her, a night light, etc. try to get her to talk about it. my daughter had a scary dream about a horse, and still sometimes confirms with me, "horsie all gone" before bed.
anyway, my two cents is, comfort her through it, support her in this, she will get through it. if it is due to fear, you can come up with some comforting story to tell her in the night when she's scared. my daughter likes to hear about her grandmother's bedtime routine, she puts on her nightgown, gets a drink of water and a snack, she gets in her cozy bed, reads her book, takes a drink, etc. i use a lot of details and it bores/comforts her right to sleep. remember to her her fears are real. this sleep thing is not linear with kids. they go through all kinds of stages. this too shall pass.... good luck!