Hate, hate, hate mine...
Exactly the same trouble.
Ladies boots are even worse...
I ended up opting for geezer boots from Gericke but even they are still too tight. I still keep trying loads on (as is the thing with women and shoes) but still cant get a pair that fits comfortably around my calf.
I am a fairly average sized 12, 5'7" (so calves should be fairly average) and a size 5 1/2- 6 shoe size.
Love alpinestars but I just haven't found a pair that fit.
There doesn't seem to be much choice for women if you are on a budget