Long-term tenant wants to sublet while she travels

[Mary Flynn Maes]

My husband and I have a house on our property that we rent out. Since we share an address, we're able to be very selective when choosing tenants, as those people become our neighbors. 

Our current tenant is asking if she can sublet the home while she's traveling out of the country for about six weeks. My understanding of California law is that if someone stays in your place for 30 days or more, that person would then have tenants rights and could become a squatter that we would have to evict. 

We're aware she's going through a rough time right now, and we would like to be able to help her out.   Is there a way to structure a sublet agreement that protects our assets and avoids an ugly situation?