It was written in her marriage contract that she had received her mahr but she has not received it and she has started to resent her husband
The mahr is the woman’s right in her marriage, because Allah, may He be exalted, says (interpretation of the meaning):
“And give to the women (whom you marry) their Mahr (obligatory bridal money given by the husband to his wife at the time of marriage) with a good heart”
“so with those of whom you have enjoyed sexual relations, give them their Mahr as prescribed”
Agreement should be made on the mahr and it should be mentioned in the marriage contract; if no agreement has been reached and it is not mentioned in the marriage contract, the marriage is still valid and the woman should have a mahr like that of her peers.
You did not explain in your question whether agreement had been reached on a specific mahr or nor, or whether it was to be paid immediately or deferred. If there was agreement on something specific, it is obligatory to adhere to that and in that case what was written in the contract about you having received the mahr does not count for anything.
The wife has the right to demand her immediate mahr and to refuse to let her husband be intimate with her until he has given her her mahr. As for the deferred portion, she should not demand it unless the time for it comes.
Ibn Qudaamah (may Allah have mercy on him) said: If she refuses to let her husband be intimate with her until she has received her mahr, and it is due to be paid immediately, she has the right to do that. Ibn al-Mundhir said: All of the scholars from whom we acquired knowledge are agreed that the woman has the right to refuse to let the husband consummate the marriage with her until he gives her her mahr. … if some of it is to be paid immediately and some is deferred, then she has the right to refuse to let him be intimate with her before receiving the immediate portion, but not the deferred portion.
End quote from al-Mughni, 7/200
See also the answer to question no. 127325
What you have to do is fear Allah, may He be exalted, concerning yourself and your husband, and to pay attention to his rights, and not let what you have mentioned make you hate him.
You should deal with this problem by finding out about the reasons for it; your guardian may have received the mahr or he may have agreed with your husband that the mahr is to be deferred, or some other arrangement. Deal with the matter calmly and with deliberation, protect yourself and your husband, try to be gentle and loving at all times, and seek your shar‘i rights without impinging on your husband’s rights.
And Allah knows best.