Assalamu ‘alaykum.
My mother bought soil that included animal dung (not sure if which animal but most likely cow dung) in it, she touched the soil and continued to touch other things such as door handles and a car seatbelt, it was also all over her clothes as she carried the package, is everything my mother touched and her clothes now najis? I had also touched the soil without realizing there was dung in it and continued to touch other objects until I smelt the dung on my fingers. Jazakallah khayr

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger.

The dung of a cow is pure according to the view of many scholars. Ibn Qudaamah said in Al-Mughni: "The dung and urine of animals whose meat we are allowed to eat, are pure." This is the view of 'Ataa', An-Nakh'i, At-Thawri and Maalik.

Shaykh Ibn 'Utheymeen said in his Fataawa collection (Likaa' Al-Baab Al-Maftouh): "The most preponderant opinion of scholars, which is the correct opinion, is that the dung and the urine of animals whose meat we are allowed to eat are pure, such as camels, cows, sheep and so on." [End of quote]

Therefore, if the "dung" you mentioned is that of a cow, then it is pure according to the most preponderant view. You can still consider it pure if you are not certain that it is from filthy animals.

Therefore, your mother's clothes did not become impure by touching that soil, nor did the things that she touched (after touching the soil).

Additionally, your hand did not become impure by touching that soil and the dung, nor did the things that you touched.

Lastly, we warn you against falling prey to whispers, because giving in to them will lead you to a great evil. So, just ignore them.

Allah Knows best.