Hi cheazypeaz
Yes, i agree with Guardian. My ex had a similar issue of witholding feelings. She thought that it is a requirement of her boyfriend to be a mind reader and read her thoughts every single time (And her thoughts changed every single second which is why she could never make up her mind). I understand your frustration, especially when things come down to her breaking plans or promises why? Because she no longer feels like it, or doesn't know or hasn't made up her mind.
How old is she? My ex was 19 and i put it down to inexperience, immaturity and plain irresponsible behaviour. I never really managed to resolve my one. I just asked her to be more decisive and to not break her promises in the future (Which made her stop giving any kind of promise in the first place). I guess, try to reassure her that you will accept her decisions and her feelings and maybe in the future she will become more open and decisive to you.
Hope above helps!!!
Don't cry, don't regret and don't blame
Weak find the whip, willing find freedom
Towards the sun, carry your name
In warm hands you are given
Ask the wind for the way
Uncertainty's gone, your path will unravel
Accept all as it is and do not blame
God or the Devil
~Born to Live - Mavrik~