According to the description of your daughter's difficulties, we recommend, before you go for an evaluation, to look for a good teacher, preferable with knowledge of remedial instruction that can work with her in the area of written expression. It's advisable to do this in concordance with the material being learned in class. It's also possible to take advantage of the summer break to work with her on the topics that she'll learn at the beginning of fifth grade. If despite the focused learning with her, the difficulties continue in expression, then it's worthwhile to consider taking her for a general didactic evaluation while consulting with her classroom and remedial instruction teacher.
Together with this, if the gap between her and her classmates is large, already now, then it's likely nevertheless to take her to be evaluated already. To receive a recommendation for a remedial instruction teacher and to receive further details regarding the evaluation process if you decide to start it now, then be in touch with the local Nitzan branch close to your place of residence.