How long since it was transplanted?

Impossible to say as there are no details included in your posting.

About 2-3 years since it was transplanted,to Montenegro. Maybe the climate does not suit her. She was better,had more leaves,I changed the soil,used hormones,cover when it is raining but nothing. Still looks the same,or worse.

Are you in the mountains or near the coast in Montenegro? You could be right, it might be your high rainfall that is the problem. What's the drainage like in the soil? Do you have it on a mound?

The drainage is good,I think. Cause I work with these palms for a couple of months,so I do not know very much about them. The problem is that the same Jubaea like this one looks great,have many leaves,and looks beautiful. So I do not know why is this one bad.

Thank you very much on advice!

Hmmmmmm...
"Jubaea is not a species that enjoys heat at all." I'd say they enjoy dry, Mediterranean heat just fine. They will grow in the central valley of California - there is a 100 year old specimen in Sacramento. Their native home is a bit cooler but similar: maybe more like Sonoma County, CA. What they cannot tolerate is hot, humid heat with high rainfall, which is why they are not found in Florida. (however, I seem to recall years ago someone found one near Orlando and posted a picture of it. It was old and in a garden shaded by live oaks. But they generally do not grow in Florida or similar high rainfall monsoonal, hot-wet season areas)
"it might be your high rainfall that is the problem"
They are found all over the Italian Lakes region, looking flawless, which in spite of being close to the Mediterranean, doesn't have a Mediterranean climate at all, having incredibly high rainfall in ALL seasons. cf: http://en.wikipedia.org/wiki/Locarno#Climate BUT, having well-drained volcanic soil and summers that are never really hot: seldom above 88F, while Florida in summer is seldom below 88F. (nights are the bigger and probably more important difference: 60F on Lake Maggiore, but with crisp mountain air, 74F in Orlando!)

In coastal Montenegro the palm should grow just fine, notwithstanding the fact that transplanting any palm that big is a major cause of stress and the plant might not survive it if not done correctly.

More water. Transplanted palms need much water. Its simply dropping the fronds it cannot support on the small rootball. You have to compensate with heavier watering. When it begins to flush well,it can be put back on average watering.
Heat is no problem. They grow in habitat surrounded by cacti and Puya's and scrublands. Wild palms with deep roots of course.

What Stanofh said, it's still getting established.