Sheila has no trouble falling asleep, but she has difficulty remaining asleep. sheila is suffering from:

Sheila has insomnia.

Explanation:

Insomnia is the difficulty in initiating, maintaining sleep or even the perception of non-restful sleep, with impairment in social and / or professional activity. Sheila has no difficulty initiating sleep, but has difficulty maintaining sleep. Sheila has insomnia.

In most cases insomnia is psychophysiological, in which predisposing factors such as increased alertness and vigilance are involved, even at night; triggering factors such as job change, loss of loved one, family and personal conflict situations, etc; and perpetuating factors such as maintaining inappropriate sleep habits (irregular bedtime, watching TV, or using computers and cell phones until late at night).