This is not very likely to be due to the lactation.  You might have encountered a variation of normal, since pregnancy and puerpueral periods tend to be thrombotic states.  

However, this is a blind comment since I don't  know the duration of lactation.  She might have encountered a thrombo embolic event during her pregnancy and still could be under heparinization which she might have forgotten to mention if the operation was held under emergency conditions, or she might have been unconscious and could not have given anamnesis. 

I am not sure for suraunding tissue but vascularisation in bone is unlikly to change changed due to hormonal dibalance.

The lactating mother mostly do depend on hormone prolactin for milk production however during the open boen surgery mostly hormone erythrpoetin plays critical role in the process of haematopoeisis especially during the first and third stages of erythropoesis where the progenitors like haemocytoblasts  ( myeloids and lymphoids) are essential

I,m not very sure that lactation could be the reason for bleeding patterns during the bone operation. But for sure, I can say that any kind of hormonal therapy must be stop before the operation procedure, in order to prevent either excessive bleeding or tromboembolic accident.