Putting a car in park while driving?

So my sister is 19 and has no experience witg actually driving a vehicle because she has epilepsy so she just got her license a couple months ago and has no experience ever being in a car. She has been saving up for a while now to buy her own, but since she got her license she has been driving my mom's old car (2001 Ford Escape) my mom just recently got a new car (2011 Ford Fusion) so my sister will be getting her own car soon, and well today she said she was driving and she that she had no brakes and while driving 50mph she put it in park in order to stop. Doesn't putting a vehicle in park while it's moving ruin the engine? She's done it before where she wasn't at a full complete stop then she put it in park and it felt like the engine fell out and we slammed into a tree. So how would it be possible to do that at 50mph? My dad checked the brakes and stuff later today and he said that the back brakes sound funny but the brakes are working fine. A few weeks ago the car was running low on brake fluid so he filled it up all the way. Is she telling the truth? I'm 17 btw and I'll be getting my license soon (permit for 2 years and driver's ed) and I'm supposed to inherit that car, so if she ruins it, I'm SOL.

It obviously is extremely dangerous to put car in park while moving, especially at 50 mph. It's good her response was to try and stop the car quickly, if she felt the brakes weren't working.
Would have been better to down shift into lower gears, but going all way down into Low would be like shifting into park, the car would slam down into low so quickly, it would SLAM down.

Usually as safety feature, while driving fast, you can't put car into park, because when cars had gear shift on the column, it was so easy for someone to jab the gearshift, and shift it up into park. So they designed the transmissions to require to slow down until car could drop into park. I once did that by mistake in car full of realatives, and the tranny merely was scraping the gears a bit, until driver shifted back into drive. Made no difference to momentum of car or riders. Just sounded a little grinding, not much.

it would be better for sister to drop gear down into a lower gear, not all way to lowest, and then apply parking break, which won't stop car, but it will slow it down a bit. The parking break is not to use in an emergency (even tho' it's called an emergency brake) to slow or stop car. It's made to merely keep car stopped while car is not running in gear. Try applying emergency or parking brake, and then drive off. You'll see you can drive, but just harder for car to move.

It's also good to put car into neutral, and then use parking brake, if there's enough opportunity to let car slow down rather than try stop the car all at once. In deep traffic, you're going to hit someone, so even slamming tranny into park won't stop you in time. In times like that, it's better to have vehicle damage than personal or human damage.

Putting car in park while driving obviously is not good for the transmission, not really the engine. But trannies are built into engines on front wheel drives, so can affect both.
I would hope your sister isn't making a joke of this. To do that to a car might be dangerous because it might not work to stop car! She could die doing that to a vehicle. So if she's done that to the same car more than once, then she doesn't need to drive that car. Let dad drive it, check it out to make sure the brakes do work all the time. Let her drive something else, and if she does same to that car, then it's probably that she's not being truthful and is just being a brat.

Its not legal for an epileptic to get a license who didn't report it to the DMV someone will die because of that you should tell the DMV save someone's life be a hero really i'm serious

Your sister should be taught to downshift (yes, even in an automatic) to slow down if there's brake failure - as long as there's enough distance between her and an obstacle.
Then there's always the emergency brake (weather foot or hand operated) - that is there for an emergency (as well as parking.)
As for slamming it into park at 50mph, that's going to cause havoc on the tires and transmission. She's lucky the car didn't spin out if control doing what she did. If she keeps this up, you are SOL.
Dad should get the brakes inspected and fixed if there's still some sort of problem with them.

I agree. Epileptic NOT cleared for the road should not be there! You have also proven that in the fact that she put an automatic (The easiest thing in the world to drive) in PARK whilst moving.