Love, cheating or anything else?

I am 45 year old officer, married and work in Govt Sector. My family lives in Lucknow, which is my birth place however due to the job compulsions I have been living alone in a Govt provided bungalow since two years. Mine is the transferable job and our place of posting keep changing every ¾ years. In the new place of posting, I was feeling highly depressed as it was very far from my native town. However after one month I came into contact with an officer co-worker whose name was Sheela. She was 25 years of age and almost 20 years younger to me. She belongs to Mathura and treated me as if I belong to her hometown. She was average in looks but has sharp features. Moreover she was master in the art of attracting the people. Every now and then she would try to make the eye contact with me. When I was on leave she would talk to me for 30/45 minutes. I was also looking for such charm and decided to get close to her. Despite of huge difference in the age that girl never ever let me realised about it. Slowly our talks turned into casual talks and both of us looks to meet at least in once in my office during office hours... Slowly I started feeling over possessiveness over her and would get jealous if I found her talking with other people. However she had this urge to talk with people laughingly. After sometimes i came to know that she had an affair going on with a coworker who was in the similar age group. Initially she tried to cover it by saying that they had brother sister relation but gradually she accepted that she was in the relationship with that boy. However that boy has to leave for a distant place due to his posting. 9 months back she get married to another boy on the direction of her father and now they are living together. As far as my relations with that girl are concerned she would keep asking me the favour related to our profession. On what’sapp she would allow me to kiss her and she would reciprocated the same sometimes. In office she would allow me to touch her cheek once and once I tried to kiss her. She would not mind touching her if it is not noticed by others. Over a period of time i.e. 02 years, i have spent more than 42 thousands rupees on her gifts on various occasions. Though she had never demanded for the gifts its me who did these favours from core of my hearts and wanted to do much more. However one day I realised that this girl never gifted me even a pen, despite of the fact that i had openly given hints to her that I would love to get any gifts or of token of love from her. Now on 20 Dec was my birthday and this time I had decided that if this time also I don’t receive any gift from her I would disconnect myself from her forever. Unfortunately this time also that girl didn’t considered giving me small gift. Now i have stopped talking to her...This girl belongs to a poor background and very junior to me. I Now I am not able to digest the fact that how can a girl outsmart a person like me on the pretext of loving/liking etc. Where is the humanity? It is something which is bothering me since long. It is not the question of gifting or exchange of favour but it is the breach of belief, trust and understanding. Who says girls are innocent.