To feel like I cant carry on saying nothing?

I have a friend who I love, she always makes me laugh and her SOH is exactly the same as mine. Many times she has been there to help out with children in emergencies, she has lent me money when I have been desperate before (I have paid her back) and generally has been a good friend. However, she has a fatal flaw, one which, up till recently, I have always been able to accept and love her anyway. Lately though it has been getting worse and now I find the whole thing unbearable. She has always always been able to steer the conversation to herself within five minutes of talking to her, normally it doesn't bother me because I know it isn't intentional and it isn't because she doesn't care about my worries, its just that listening and giving advice is not one of her strong points. She has a partner who she met about 8 months ago after splitting with the father of her younger two children and since their relationship began they have been on and off around five times. Every time it happens she plunges into a deep depression where she either shuts herself off or becomes totally dependent, melting down and begging me to come round so she isn't alone, even if it is the only night that week I have to spend with my husband, and I go because I AM good at listening and giving advice.After recently losing my job we both decided to try and start a business together and within a month of starting it she said she couldn't be bothered and left me high and dry with commitments I had already made because she was supposed to fulfil them, when they are on, I never hear from her, she is always with him and when I do see her all we ever talk about is her and her life and her problems. Am being unreasonable to feel like I can't carry on this way or should I just be putting it down to the fact that she is in a new relationship?