She may be ok. We took DS when he was only 3mths old and he didn't really like it (ended up crying when you were suppose to be quiet) but at the time DP had him in the front pack and he may have just wanted to be with me.
They had all the people with children go in one boat so others didn't get disturbed. There were a few other kids there and they all seemed to enjoy it. And I am sure that if we took him now he would love it.
It is really up to you. She may be ok or she may not. There is only one way to find out