Absolutely , you can criticise someone constructively. Buddhism in no way teaches us to be pushovers. However, the Buddha mentioned from the (AN V (From The Patimokkha, Ñanamoli Thera, trans.))
Source : https://www.accesstoinsight.org/ptf/dhamma/sacca/sacca4/samma-vaca/index.html
In order for your actions to be skillfull you have to admonish the person hurting you or others very skillfully.
How to admonish another skillfully
"O bhikkhus, a bhikkhu who desires to admonish another should do so after investigating five conditions in himself and after establishing five other conditions in himself. What are the five conditions which he should investigate in himself?
 "Am I one who practices purity in bodily action, flawless and untainted...?
 "Am I one who practices purity in speech, flawless and untainted...?
 "Is the heart of goodwill, free from malice, established in me towards fellow-farers in the holy life...?
 "Am I or am I not one who has heard much, who bears in mind what he has heard, who stores up what he has heard? Those teachings which are good alike in their beginning, middle, and ending, proclaiming perfectly the spirit and the letter of the utterly purified holy life — have such teachings been much heard by me, borne in mind, practiced in speech, pondered in the heart and rightly penetrated by insight...?
 "Are the Patimokkhas [rules of conduct for monks and nuns] in full thoroughly learned by heart, well-analyzed with thorough knowledge of their meanings, clearly divided sutta by sutta and known in minute detail by me...?
"These five conditions must be investigated in himself.
"And what other five conditions must be established in himself?
 "Do I speak at the right time, or not?
 "Do I speak of facts, or not?
 "Do I speak gently or harshly?
 "Do I speak profitable words or not?
 "Do I speak with a kindly heart, or inwardly malicious?
"O bhikkhus, these five conditions are to be investigated in himself and the latter five established in himself by a bhikkhu who desires to admonish another."
In short , investigate whether you are doing it out of anger our out of a pure intention to protect yourself and the other person as well .Make sure that it is true that the other person is indeed gossiping about you and this is not just your assumption . And then ask yourself whether it is beneficial, to all concerned.If all these three conditions are fullfilled then pick a right time to speak it.