PORTLAND, Maine — A former nurse at Brunswick and Lewiston hospitals pleaded not guilty in Cumberland County Superior Court on Tuesday to bilking an elderly couple out of $274,000 in an effort to finance a “boutique” senior housing complex in downtown Brunswick. Amy McLellan, 61, of Brunswick pleaded not guilty to misuse of entrusted property of a vulnerable person more than $10,000 and theft by unauthorized taking of more than $10,000, both Class B offenses for which she faces a maximum of 10 years in prison. Prosecutors charged McLellan with befriending a then-92-year-old man suffering from Parkinson’s disease while he was a patient at Central Maine Medical Center in Lewiston, where she worked as a nurse, then convincing him to give her power of attorney and, ultimately, to drain his savings account to allow her to finance The McLellan complex on Cumberland Street in Brunswick. Since purchasing the building for just more than $1 million in August 2016, McLellan has renovated the former Skofield House nursing home — and original Brunswick Hospital — at the corner of Cumberland and Union streets into The McLellan, an upscale senior living complex with on-site skilled nursing care. After receiving a report from an employee of McLellan’s, Brunswick police and the Financial Abuse Specialist Team of the Maine Department of Health and Human Services began an investigation.