Couple of drops, to a human being our size is fine. To a chameleon, couple of drops means a lot of blood. To be safe, better to get her check to the vet. You don't want any scar develped that might interfere with eggs laying.
Just noticed this thread and thought I would add our experiences with this topic...
We actually have seen a lot of this - spots of blood when breeding. We have seen it with chameleons, bearded dragons, and blue-tongue skinks (the most).
The first time was with a mating pair of sambavas. We panicked. Our vet examined both and told us he could find no problems but to watch them both carefully. As it turns out, nothing ever came of it. The male sired lots of young'ns and the female had several clutches.
We saw it again a few times and always took every precaution possible. We then saw it happen with beardies - but only once. Then we started breeding skinks..... wow, can they bleed! It finally became clear what was happening. The male was injuring his hemipene - and bleeding ensued.
Think about it this way: the male has to wrangle his positioning just right. If it is a chameleon - that could mean moving his boy bits over a rough stick. Ouch! With the beardeds, it was the same thing - the big chunk of wood in the cage. But with the skinks (even bred on towels) it turned out to be the claws of the females' back feet. We have seen this happen several times. If this does happen with the beardeds or skinks, we always give cool, sucrose baths (sugar water) afterward - then rinse the poor fella off so he isn't sticky.
When breeding reptiles, one needs to be prepared for such happenings and the possibilities of prolapses as well. Prolapses are really unpredictable!