Switching to triples can indeed be a helpful way to get a couple more weeks of LP in for many women. It’s not a necessary switch however and it’s only going to extend the LP a few weeks, not months or anything.
That would depend on the increases she was doing, but using 5# for squat and DL and 2.5# for press and bench usually needs to happen fairly early for most women. But again, there’s not really a stock “all women do this” answer.