Urgent: How to handle this situation

Hi ppl,

I ve got a sort of v irritating situation and thought of asking suggestion from you ppl.

Here it goes. I ve a colleague X (female) who is in the same task group as mine. She never talks to me in public, never smiles at me even if I try doing so. But when alone she used to talk to me. I initially did not understand this and I was always sweet to her. Now adays we are made to sit in the same place and she hardly looks at me. She has her group of friends with whom she hangs out. She was in search of a home and approached me. I helped her a lot and got her a home too in my appratment (infact she lives next door). She used to invite ppl for party etc etc but I am just a wall away and she had never invited me even once. When others come and ask me why didnt you come inspite of she inviting you I was shocked. She had lied to ppl that she invited me too. And whenever some plan for an outing they used to ask her to inform me but she never does and one fine day the common friend told that she asked that X person to call me but X has told that am not in home...But I was in my home only.

Recently she got married 3 months back and she invited ppl to her home for party, reception etc etc but I was not invited for any...Nor did she even introduce her spouse to me...But whenever she needs she knocks at my door, whatever help she needs she easily extracts from me...Of late all ppl who were talking to me also started restricting themselves...

Now suddenly she had called me over for dinner @ home along with her other friends through mail (Even during my B'day this yr, she never wishes me in person. I ll sitting next to her and still she sent me a blank mail saying HAppy B'day)..Iam not able to judge this person...Since she is not doing anything openly....I actually dont want to go for dinner today...How to avoid her subtly? What are your suggestions? Should I go??