Does she have to repeat the prayers that she offered in a wrong manner because she was new in Islam?

If someone is new in Islam and is not able to do what Allah has enjoined upon him of purification, prayer or fasting in the prescribed manner that absolves him of accountability because he is unaware of the rulings, and does not have sufficient, sound means of acquiring sound knowledge, so he thinks that what he is doing is what is prescribed, then when it becomes clear to him that he is wrong, he follows the truth and adheres to Allah’s rulings and what He has prescribed, then he should not be instructed to repeat what he did imperfectly of the duties enjoined by Allah. He is excused for his ignorance, because he only did things the way he did them before because he was ignorant and made mistakes, and he is to be excused for that, because of the general meaning of the verses (interpretation of the meaning):

{And never would We punish until We sent a messenger} [al-Isra’ 17:15]

{And never would your Lord have destroyed the cities until He had sent to their mother a messenger reciting to them Our verses} [al-Qasas 28:59]

{Our Lord, do not impose blame upon us if we have forgotten or erred} [al-Baqarah 2:286].

Ibn Majah (2034) narrated that Abu Dharr al-Ghifari (may Allah be pleased with him) said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “Allah has forgiven my ummah for what they do by mistake or out of forgetfulness, and what they are forced to do.” Classed as sahih by al-Albani in Sahih Ibn Majah.

Al-Hafiz said in al-Fath (5/161):

This is a great hadith. Some of these scholars said: It should be counted as half of Islam, because deeds are either done intentionally and by choice, or they are not. The latter either happens by mistake, or out of forgetfulness, or because one is forced to do it, and this category is forgiven, according to scholarly consensus. Rather the scholars only differed as to whether what is overlooked is the sin or the ruling or both? The apparent meaning of the hadith points to the last of these, and whatever is exempted from that, such as murder, has its own evidence. End quote.

Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said:

If someone prays without deliberation, and does not know that that is obligatory, there is a difference of scholarly opinion regarding him: does he have to repeat it after the time for the prayer has ended or not? There are two well-known views, both of which are views in the madhhab of Ahmad and others.

The correct view is that in such a case, the person is not required to repeat the prayer, because it is soundly narrated from the Prophet (blessings and peace of Allah be upon him) that he said to the Bedouin who prayed badly: “Go and pray, for you have not prayed,” two or three times, then the man said: By the One Who sent you with the truth, I cannot do any better than this, so teach me what will suffice me in my prayer. So the Prophet (blessings and peace of Allah be upon him) taught him to pray with deliberation. (Agreed upon). And he did not instruct him to repeat whatever he had prayed before that time, even though he said, By the One Who sent you with the truth, I cannot do any better than this. Rather he instructed him to repeat that prayer, because the time for it had not yet ended, so he was instructed to offer that prayer on time. But in the case of prayers for which the time had ended, he did not instruct him to repeat them, even though he had omitted some of their obligatory parts, because he had not been aware that that was required of him. Similarly, he did not instruct ‘Umar ibn al-Khattab (may Allah be pleased with him) to make up the prayers that he did not offer because of being in a state of janabah, because he was not aware that he could have prayed after doing tayammum. And in the case of the woman who was suffering from istihadah [prolonged non-menstrual bleeding], she said to him: I suffer from extremely heavy bleeding that prevents me from fasting and praying, he instructed her to do wudu’ for each prayer, but he did not instruct her to make up the prayers that she had not offered. By the same token, in the case of those who ate during Ramadan until one of them could distinguish a white thread from a black thread, so they ate after dawn had broken, he did not instruct them to repeat their fasts. These people were unaware of what was obligatory, but he did not instruct them to make up what they had failed to do when they were ignorant of the rulings. Moreover, a disbeliever is not instructed to make up what he did not do when he was in a state of disbelief and ignorance, in contrast to one who was aware of what is obligatory, but failed to do what is required because he forgot; such a person is to be instructed to do it when he remembers it."(Majmu‘ al-Fatawa  21/429-431).

Al-Suyuti (may Allah have mercy on him) said:

If someone is unaware of the prohibition of something of which most people are aware, the claim of ignorance cannot be accepted from him, unless he is a recent convert to Islam, or he grew up in a remote wilderness where people may not be aware of these prohibitions, such as the prohibition on zina, murder, stealing and alcohol, and on speaking during the prayer or eating when fasting."(Al-Ashbah wa’n-Naza’ir p. 200).

Based on that, you do not have to repeat those prayers that you offered before. Praise be to Allah, Who has guided you to the light of Islam. We ask Allah to enable us and you to adhere firmly to the path of Ahl al-Sunnah wa’l-Jama‘ah.

You should contact Islamic centres which are active in educating people and teaching them about their religion, to learn the true religion and how to adhere to the path of the righteous early generations.

You should also read Islamic websites that follow the path of Ahl al-Sunnah.

And Allah knows best.