She is known for being a nice-Nelly.

I saw a high-nelly parked outside the shop.

I saw a High Nelly parked outside the shop.

She is always complaining and seeing the worst in every situation. She's such a negative Nelly.

I saw a high nellie parked outside the shop.

She is such a nervous Nellie that she worries about everything.

She is such a nervous-Nellie when it comes to public speaking.

She is such a Nervous-Nellie when it comes to public speaking.

She is such a Nervous Nellie.

She is such a nervous Nellie, always worrying about everything.