How to get proof of subletting

[Bela B.]

How do I as a landlord prove subletting? I received a violation notice of house sharing this past Feb but my lawyer says it has to be violation happening now (I should have evicted her then) but instead I started mediation through LA County DCBA where she actually admitted to subleasing and said she will continue to sublease knowing I cannot use mediation conversations in court.  Otherwise she denies subleasing on email or other communication and says the people there are friends/family housesitting, etc. What do I need to prove subleasing in court? Is an advertisement online of the property enough or do I need an actual copy of the sublease? Not sure how I would get that...