Final answer:
Lizzy is likely in REM sleep if she has nightmares or possibly in NREM stage 3 sleep if she experiences night terrors, as both can cause distress but occur at different sleep stages.
Step-by-step explanation:
If Lizzy fell asleep about 2 hours ago and is experiencing nightmares, she is likely in the REM (Rapid Eye Movement) stage of sleep. This stage is commonly associated with vivid dreams and nightmares due to the increased brain activity that occurs.
However, if Lizzy is experiencing more of a night terror, which is characterized by a sense of panic, screaming, or attempting to escape from the immediate environment, she might be in NREM (Non-Rapid Eye Movement) sleep, and more specifically, during one of the deep sleep stages such as stage 3 sleep, where night terrors are more likely to occur. Unlike nightmares, individuals typically do not recall night terrors the following morning. While nightmares and night terrors both can disrupt sleep, they are distinctly different experiences and occur during different stages of sleep.