In the name of Allah,
As for Kissing one’s spouse while fasting in Ramadan, this has been discussed here.
Imam An Nawawi (may Allah have mercy on him) uses a quote from Qadi Iyad to show some possible reasons why she smiled.
Qadi Iyad said that some people thought her smile showed surprise at anyone who thought otherwise. Others said she was surprised to hear herself describe this hadith, as some people, especially women speaking to men, might feel uneasy doing so. She was obligated to convey this information, so she was required to mention it. Thus, she was puzzled. Others said she smiled to remember how near she was to the prophet and how well he treated her. She may have also smiled to suggest that she was referring to herself, making her audience more likely to believe her statement.’[ii] [paraphrased]
May Allah’s peace and blessings be on the last and final prophet
[i] Sahih Muslim 1106a
[ii] Sahih Muslim With Full Commentary By al-Nawawi, Vol 6 English, Al-Minhaj Sharh Sahih Muslim ibn al-Hajjaj Sahih Muslim, With Full Commentary By Imam Al-Nawawi, Translated And Edited By Adil Salahi, The Islamic Foundation & Islamic Community Milli Gorus (ICMG), Australia Distributed By Kube Publishing, Page 446