Scared of room

My daughter just turned 3 a few days ago and for the last couple of weeks she’s been acting...different at bedtime. She’s never really liked sleeping in her own room but she would sleep through the night after we got her to sleep. I would put her in her bed and sit in the living room in case she needed me and when she’s get out of bed I’d take her back and reassure her and she’d fall asleep on her own. But now she wakes up multiple times a night. She comes downstairs to my room and refuses to go back to her room like she’s scared. She hasn’t actually said it’s scary but she’s not the type of kid to tell us how she’s feeling because she gets embarrassed easily. She did tell me tonight that someone or something in her room won’t leave her alone. I couldn’t make out who/what it was because she was crying and when I asked her what she said she started ignoring me and hasn’t said any other word about it. She’s been talking about monsters recently but in a playful way. She’ll pretend to be a monster and chase us around and she’ll laugh. So I don’t know if she’s starting a fear of monsters or if it’s something else. Any advice on how to get her to stay in bed and ease any fears she might have? I feel like something is scaring her but she won’t tell me what it is. We leave the hall light on every night because my son prefers to sleep with the light on. I’m thankful for any advice!