“She is highly motivated, reliable, and pleasant to work with.”

Your former employee is applying for a new job and has asked you to write her a letter of recommendation. You want to write positive things about her. You write:

She is highly motivated, reliable, and pleasant to work with.

(someone) is highly motivated

A "motivated" person not only works hard, but is also proactive, which means that they look for things that need to be done without being asked. People can be "motivated" to do work, or to do other difficult things like sticking to a diet:

The key to successfully accomplishing one goal after another is staying motivated.

The most common adjective used together with "motivated" is "highly". It means "very", but "highly motivated" sounds a lot more natural than "very motivated". Some other adjectives that go well with "highly" are:

highly unlikely

highly skilled

highly competitive

highly qualified

highly regarded

(someone) is reliable

"Reliable" people are easy to trust for things like coming to work on time, doing what you asked them to do, keeping their promises, and so on.

pleasant to (do something with/to/about/at/etc.)

"Pleasant" is similar in meaning to "nice". It sounds a little more formal and more intelligent than "nice".

You can talk about how something is pleasant with the phrase "pleasant to ___":

Kendra not only did the job, she did it well, and she was pleasant to be around and tremendously courteous.

She certainly is pleasant to look at.

He's so pleasant to talk to.