It can be done but not with much certainty as to how many times... is she initially looking to extend it here in Nanjing?
Also worth looking at some agents online who can always advise on the current situation.
Officially, according tho the current visa regulations for those applying outside of China, a 6mth tourist visa is only for those married or with other family etc here whilst others would at best get 3mths. If your friend had originally gotten the 3mth visa then for certain you can extend it once no trouble but very unlikely to get a 1mth extended enough times to get 6mths up.
Again, maybe an agent can do it.
Sounds like an interesting trip,
Ami