My friend (Muslim) have 50 yogurts with gelatine (not halal, to use for herself). She is asking is it permissible to her to give this yogurts to her non-Muslim mother, her mother always spends money on such food. Or it will be better to feed cats or dogs with it?Please, explain us how to be in such situations, for ex.: can we give silk clothes to non-Muslim, or perfumes (alcohol); or better to put such things into garbage? what is the opinion of the scholars?

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

If gelatin is derived from dead animals or forbidden animals and so on, then it is Haram to eat this 'yoghourt mixed with gelatine.' This ruling applies both to Muslims and non-Muslims. So, we think you have to ruin it or to feed animals with it.
As for giving silk clothes as a gift, we state that it is Halal, whether you give them to men or women. But, it is Haram for men to wear them.
It is reported by Bukhari and Muslim that Allah's Messenger (SAW) gave Umar a silk dress and said: "I did not give you to wear it." So Umar gave it as a gift to a polytheist brother in Makka.
Imam al-Nawawi (may Allah's mercy be upon him) said: 'this Hadith indicates: (1) that it is legal to have good relation with non-Muslim relatives and to treat them kindly; (2) it also indicates that it is legal for a Muslim to give a non-Muslim some gift, and (3) that it is legal to donate silk clothes to men but it does not mean that it is Halal to wear them since the Hadith states that the silk was given 'as a gift not to be used as a dress.' The Prophet (Sallallahu Alaihi wa Sallam) sent such a gift to Umar, Ali and Usamah (RAA), and said, get benefit from it and do not wear it.'
Allah knows best.