When she started lifting she had just one plate each side!
Other days you are just feeling weak, lethargic or just plain not intersted. These are days that you should also be seeking a PB. I know your probably thinking that there is no way you are going to do this if you aren't feeling strong or motivated but it is all in relation to your frame of thinking. what's to stop you grabbing a kettlebell and going for the most consecutive snatches you have ever done. Or powercleaning that 60kg weight more times than you have done in a 3 minute period. Regardless of what it is you are attempting by constantly looking for new and novel ways to do something you haven't done before your body has no choice but to respond.
When you become a serious lifter the only thing that slows your progress is your mind. If you can overcome this by re-framing things then there is no reason, regardless of what current physical stage you may feel that you can't continue to push yourself into a zone your body has never gone to before.If you are having one of those days where you are just feeling completely hyped up and super strong than by all means go for that PB. One piece of advice is to not jump too far ahead. Take small increments. The reason is that mentally the success of each consecutive lift acts as further motivation to go for the next one. You will be surprised how far you can push into new max territory when you are making only 2.5kg increments. There are times I have pushed a good 3 times into a new PB using that type of system. your previous best may have been say a 200kg deadlift. Don't jump to 210kg, do a 202.5kg. You will find that if you lift that it spurs you to go again and go for a 205kg. If you jumped to the 210kg and miss it badly you'll be surprised how you then can't do the 202.5kg. It's as if you have just hardwired your brain to think of failure after that attempt. go small and build it up and you will be amazed how the momentum of success can go on for weeks.Happy (brutal) lifting!