Is it wrong for two women to kiss each other on the lips... There is no sexual attraction among them they are just as sisters.. They are straight and very sure about this.. Is it wrong for them to do so?
Likely it's not allowed.
Kissing lips is more common with the older generations and also more common for warmer cultures (Arab or Latin cultures)
I've seen parents, grandparents do this ie it's usually when a junior member of the family makes a senior member very proud.
It's very odd for two adults to do this. It's generally recommended to show your affection for other believers by hugging and kissing them. But there are certain limits
I selected these two narrations from: Usul Kafi, volume 2, Chapter of kissing (تقبیل):
مُحَمَّدُ بْنُ یَحْیَى عَنِ الْعَمْرَكِیِّ بْنِ عَلِیٍّ عَنْ عَلِیِّ بْنِ جَعْفَرٍ عَنْ أَبِی الْحَسَنِ ع قَالَ مَنْ قَبَّلَ لِلرَّحِمِ ذَا قَرَابَةٍ فَلَیْسَ عَلَیْهِ شَیْ ءٌ وَ قُبْلَةُ الْأَخِ عَلَى الْخَدِّ وَ قُبْلَةُ الْإِمَامِ بَیْنَ عَیْنَیْهِ
There is nothing against one whom kisses his kin or his brother (in faith) at his cheeks or his forehead
وَ عَنْهُ عَنْ أَحْمَدَ بْنِ مُحَمَّدِ بْنِ خَالِدٍ عَنْ مُحَمَّدِ بْنِ سِنَانٍ عَنْ أَبِى الصَّبَّاحِ مَوْلَى آلِ سَامٍ عَنْ أَبِى عَبْدِ اللَّهِ ع قَالَ لَیْسَ الْقُبْلَةُ عَلَى الْفَمِ إِلَّا لِلزَّوْجَةِ أَوِ الْوَلَدِ الصَّغِیرِ
Kissing the lips is for no
one other than your spouse or (your) little children