I would highly recommend learning from a professional and taking a course like the ones offered at
FTW Ranch. Hunting NA whitetail will be nothing like taking on a lioness other than the act of pulling the trigger.
Make sure you have a reliable rifle, premium ammo, proper hunting equipment for the task and most importantly...know how to use it. Practice from sticks, standing (unsupported) and kneeling at distances ranging from 75 yards to 10. Preferably on a target moving towards you.
You could also set up multiple targets (say 4), starting at 75 yards, then 50, then 25, then 10...shooting them farthest to closest in rapid succession with a hit on a 3"x3" target being the goal on the last three targets. I'd be looking for a 1" bullseye on the first shot at 75 yards.
Highly recommend a RDO if you don't already have one. The other option would be a scope that's lowest magnification setting is true 1x for "both eyes open" shooting. Also like to see that scope mounted in QD rings. Not that you will have time during a charge to remove it, but if the lioness were to run away after the first shot, you could take it off for the tracking and followup shot.
Practice and then practice more. Dry fire practice at least 10x more than you live fire. Get to know your rifle and create muscle memory of how to reload. Strap on all your kit and practice taking cartridges off your belt and reloading. Do this over and over until it's second nature. Your efforts will be rewarded.