I had a mom several years ago with severe leaking that started a few months
postpartum after finally getting through a very trying initiation phase:  sore
nipples, mastitis, thrush, overactive MER, sucking difficulties.  This mom would
spontaneously let down and leak several times a day to the extent that milk
would spray across the room if she were not wearing clothing.  The only
significant change during this time period was that this mom had begun binging
and purging (vomiting).  A colleague knowledgeable about bulemia found it to be
associated with forceful milk ejection.  Moms are not always candid about this
type of problem, but you could ask her if she is vomiting a lot.
        I have not heard of leaking with a new pregnancy, often milk supply
declines slowly by mid-pregnancy.  Thyroid disorders seem to be common in
postpartum women, hyperthyroidism could cause a huge increase in milk supply.
You could refer the mom to her MD for blood tests for prolactin, T3, T4 and TSH
levels.  Is it possible that the baby is taking less milk suddenly due to
development (walking and being too busy to nurse?) or an increase in solid
intake?  If this is the case, the leaking should stop pretty quickly as mom
adjusts to the lower demand.  Could the mother possibly be eating a lot of
licorice or taking a drug or herb that affects smooth muscle tone?  This could
conceivably relax the circular muscles that keep milk in the breasts...
Keep me posted,  Cathy