“She may have behaved that way externally, but internally she was thinking something completely different.”

Sure! Here are a few examples of how you can use "internally" in a sentence: The company is working to improve its processes internally before expanding to new markets. She was struggling with her emotions, but she tried to deal with them internally. The organization is conducting an internal investigation to determine the cause of the data breach. He was promoted to a higher position within the company after showing strong leadership skills internally. The company has a strong culture of collaboration internally, which has helped it to achieve great success. I hope this helps!

It's an adverb, so it needs to define a verb, an adjective or another adverb. This memo should only be circulated internally. The adjective "internal" is used much more often. This memo is only for internal circulation. The internal organs include all the major organs except the skin. And don't confuse "internally" with the similar-sounding "eternally." If you could do me this favor, I'd be eternally grateful.