am i loosing my friend?

I know this must seem an immature question considering my age and life experiences.

but here goes.

My dearest and best friend lets call her beth over the last year or so has been somewhat distance. Now this I do know she has been having a hard time with certain illnessess that are causing her to become less active and sick all the time, she complains of constatn fatigue, the doctors suspect lupus. any way I have been friends with her for over 11 years, she has been my rock, my angle eveything you could ask for. I appointed her as god mother to my daughter and have always helped her in any way im always there for her. I even allowed her to be at the birth of my first born son, it was a special moment and my husband and myself were so thrilled to have her there. But not to long ago when i was visiting her, when she was having a sleep her BF and I were outside and he said "did beth tell you that I proposed" I was so shocked when he told me this and I said no she did not he too was quite shocked as he said but your her BFF i dont know why and im sorry if you didnt know. I shook it off and said dont worry and congrats I was sincerely happy for them. But she never ever told me I waited for 4 weeks for her to tell me after her BF told me and still did not say anything, I eventually plucked up my courage and said i know you are engaged and I wanted you to know that I know and I hope there are no hard feelings, she didnt really come up with an excuse as to why she couldnt tell me. But ever since then when I ring, leave a message, text message she never responds, when i do eventually hear from her she acts like she has missed me and seems genuinly happy to hear about me and my family. She always says things like i really want to travel up to see you and the kids but Im so sick, or I cant get the time off or I cant afford it..yet she is always travelling interstate and just recently got back from thailand. I cant understand this behaviour. why she claims to me how much she loves me and my friendship ect ect but lies to me and hides from me in truth. I miss my friend so very much and feel even more sad becuase I can never have a cry on her shoulder when i need her. Is she genuine, or should I just walk away and realise that she does not want to be friends with me any more…:(