Sounds very odd to me and certainly a BS excuse - she must’ve had jiz on the carpet before now given how long she’s been doing this - pre-cum or a spent load. She also lists Bukkake, CIM, Snowballing etc. on her profile, so she’s certainly not averse to a bit of cum here and there.
Unless is was a £50K Persian rug, are you sure it wasn’t something else that made her say this/act this way - either on this occasion or when you saw her previously?