Lots of info to work on there! Is it latex backed? Does it have a fabric edging around it?
I would presume it is looking dirty so probably a waste of time adopting the VLM approach, which is the only "safe" way. If I could get the customer to agree to a "fix it or bin it" approach I'd use a saturation clean the same as any other rug, but you need to make sure you won't end up being blamed if it goes wrong. Legally if you ruin it you own it, but 99.9% of customers will accept the risk themselves if you explain it professionally enough. You have to work it round so they tell you to clean it, so the onus is on them. Your judgement call entirely, as you are on shaky ground in liability/legal terms
You'll either come out a hero or have to sheepishly take it back broken and hope she accepts it was a goner anyway and shrugs her shoulders.
It might lose colour, end up patchy, suffer browning, or most likely it will go wavy but you could block it. Personally unless I was 100% confident with this sort of thing I'd leave it alone

The money has to be right as well, might be £200 worth of work depending on the size of the runner and how much work needed