All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
You have done well by showing kindness and hospitality towards this woman and her daughter, because it is both an act of kindness and keeping ties of kinship, given the family relations between you, which makes the reward for your kindness greater. On the other hand, it is vile of them to return your kindness with such abuse, especially their making fun of religiousness and Hijab. This is a very serious act that may take the doer out of the fold of Islam; Allaah, The Exalted, says (what means): {And if you ask them, they will surely say, "We were only conversing and playing." Say, "Is it Allaah and His verses and His Messenger that you were mocking?"/Make no excuse; you have disbelieved after your belief. If We pardon one faction of you - We will punish another faction because they were criminals.}[Quran 9:65-66]
This woman and her daughter should be given advice about the gravity of their actions. If they reject the advice, then they should be deserted if this is likely to have a positive effect on them.
It should be noted that the guest is entitled to hospitality for a period of three days, and anything beyond that is charity bestowed upon him by the host. Moreover, the guest should not cause any inconvenience to the host; please refer to Fataawa 92645 and 104798.
You should gently indicate to this woman and her daughter that you are expecting other guests and that there would be no space for them along with them. You are also advised to seek help from Allaah and be patient; the best end is for those who adhere to patience. And Allaah is with the doers of good.