She accumulated wealth through begging and built her house with it; how can she repent?

Firstly: undoubtedly begging and asking of people when one is not in need is haram.

Shaykh al-Islam Ibn Taymiyah said: There are mutawatir hadiths from the Prophet (blessings and peace of Allah be upon him) which indicate that it is prohibited to ask of people except in the case of necessity."(Majmu‘ al-Fatawa  8/538).

We have previously discussed the prohibition on begging and the circumstances in which it is permissible, and the evidence for that, in the answer to question no. 104781 .

Secondly: the wealth that has been accumulated through begging and asking of people without being in need is unlawful wealth, because it was taken in a manner that is not permissible according to Islamic teachings, as the one who gave it in charity to the beggar only gave it to him because he thought that the one who was asking for it was in need and poor.

Based on that, this woman must get rid of this wealth by spending it on charitable causes and giving it to the poor and needy on behalf of those who donated it.

Whatever has been spent of this wealth, no action is required regarding it.

If the woman is in need, then she may take of it as much as she needs and will suffice her. That includes what she has bought with this money of dwellings and shops and the like. But she should limit it to as much as she and her children need, and get rid of the rest.

Please see the answer to question no. 78289 .

And Allah knows best.