Have you tried spying Chrome as a windows application? If that did not work then, unfortunately, nothing else will work because Blue Prism does not support Chrome yet. Another thing you can try is to write a VBO script or something that will clear the cache and cookies in chrome and use the bot to launch that script. Another thing you can try is to use another application or tool that can clear chrome cache and cookies and use Blue Prism to control that application/tool. CCleaner is a tool that will clear Chrome and IE cache and cookies at the same time, you can play around with the setting of that tool and once saved it will always keep those setting so you can just use Blue Prism (bot) to open that tool and use the bot to click the run button.
Hope this helps 🙂