I legitimate reason for sharply reducing communication ought to have been provided in a forthright manner, if she had one. (Could be workplace upheaval, family problem, medical problem - some might be things she feels are private.)

Asking you to call and then not answering strikes me as a childish game with no good explanation.

The best I can come up with is she lost momentum or excitement toward you - while that does not reflect well on her emotional stability (or your chances), do a lesser degree I would see it as within a range I might call normal.

Personally, I would not travel to meet such a probably flaky person.

I would give her some requirements, such as fulfilling her promises about her availibity. Not calling often and not being availible are okay to me; but making and then breaking promises is not.

I suggest giving up on this one.