If one of my girls has already got 85% cloudy tric...

that' can't be said, as every plant matures and grows differently.. if you're at 15% already, then depending on the high you want you might want to cut her.. remember that the type of high depends not only on the strain, but also on the state of the trichomes.. the main question you should ask yourself is "what kind of high" do you like? Should it be more of an "active" head high for during the day, or more of a "body high" which pushes you into the couch and makes you sleep well? Once you know that, you should look at the strain you're growing.. If the plant you grow is a pure "indica" hybrid, the standard high will lock you more into the couch by default, while a pure sativa would give you more of a head-high (the basic sativa-indica difference), but then of course there are still a lot of hybrids in between. This is just a general rule, but it also depends on time of harvest. When it comes to trichomes you know they go from clear to milky and then to amber, and you stated it's already at 15% amber. In general if the plant one is an indica-heavy plant (so more of a couch-lock), if you want a head-high, you'd be best off harvesting when around half are still clear, and half are milky.. If you want a body high, then most should be milky and some amber. If 20 or 30% or more of them are amber, it'll just be definitely in the body-high area, pushing you into the couch (and as always, don't wait too long or they'll fall off the plant). In comparison if this were a sativa, then even even when the trichomes are full milky it should still give you more of a head-high, and to get more of a body-high effect you'd need to wait until there are a lot of amber trichomes. The hybrids are obviously somewhere in between and the white widow is a hybrid. So it's basically up to you, what you prefer and the type of strain you grow, but i wouldn't wait too long.