What should a committed girl do when suffering from severe self-flagellation and fear of her deeds not being accepted, as well as the whispers of showing off (riyaa'), due to remembering past sins and former ignorance of Islamic rulings, and what is the way to overcome these negative thoughts?

Have a good opinion of Allah, for Allah is as His servant expects Him to be, and He is the Most Merciful of those who show mercy. You will not see anything from Him except good. Abandon the negative thoughts that Satan casts, praise Allah for guidance, and seek help in this through Islamic knowledge, the company of righteous women, dhikr (remembrance of Allah), and du'a (supplication). Do not repeat your prayers; there is no need for self-flagellation. If necessary, consult a psychiatrist.