I would not call that living solely on bitcoins, nearly none of the merchants accept bitcoins there.
If she gets a crypto backed card with visa membership it would be a lot easier to live a normal life.

After a few minutes of googling I found two articles about the said challenge. Using image search on the image link shared by the OP would lead you to a youtube video of her doing the challenge.  

https://news.8btc.com/chinese-girl-challenges-to-survive-21-days-with-only-0-21-bitcoin-can-she-make-it
http://tech.chinadaily.com.cn/2018-09/11/content_36896437.htm

I was going to suggest this too (bitcoin debit cards) but you beat me to it.

thrown 'into a strange city'
whatever the currency is.. the first few days will be living by the skin of your teeth learning your new surroundings.

but there actually are hundreds if not thousands of people that work and live but have NOT received an income in fiat for at least a year

i for one have been living happily on bitcoin since 2012

If its purely Bitcoin to spend 24/7 then that's going to be hard since there's not much merchants that accept Bitcoins yet. I my self cannot challenge my self to live with just Bitcoins, I just can't specially in a country where Bitcoin is still an alien word to many. There's no store that sells meat or fish in exchange for Bitcoins. A few weeks ago I visited Thailand and the money I spent there came from the profits and earnings in Bitcoin. Unfortunately I have to convert it to fiat and lost around 0.012BTC for the fees.

This thread gave me an idea. Here we have a delivery service called Honestbee. You can buy grocery from you favorite store online and it will be delivered within the day. Maybe we can add Bitcoin as a pay option.

also stayed at mcdonalds and ate left over burgers
ended up in hospital with hypoglycemia
1. when in china you can hang around many restaurants and eat left overs from many different varieties. why only at burgers.. dang. even if you stayed at mcdonalds, they do serve more than just burgers.. so again why only eat burgers
2. if she had hypoglycemia after just 3 days. i guess she has an underlying medical problem and should have thought about and naturally known about trying a varied diet. so again why only burgers... EG stand near a vegetarian restaurant or dare i say it a chines restaurant

seems her choice of location to be in was the flaw. not the currency.
even with no currencies of any type. i would atleast explore the variety of locations and see whats available

your not going to find many bitcoin hotels, restaurants if you decide to go on strike and just sit in one restaurant for 3 days only eating leftovers of one food type

maybe the chinese lady should have tried 'beccy and austin' (life on bitcoin) as a tutor before doing the project, they done well and lasted longer

In normal circumstances she might not have survived. But her friends helped her out with the necessities. Still I agree with your post. It will be much easier if she gets a Visa or Mastercard debit card, which can be topped up with Bitcoins. I myself owns one.

I think it is a smart way to live your life with limited amount of money while if i say about my self then i have more expenses than this girl if she lives with this amount she will become a good saver and rapidly she can further invest money in bitcoin and she can make more money so we can say that bitcoin is helping people.

It would be very interesting,if somebody tries to live 1 month with 1000 USD worth of gold only.By "gold" I don't mean gold coins,but one big piece of gold.Would it be easier,compared with bitcoin or no?
How to cut one big piece of gold,where to sell it(most of the gold buyers cheat).
That would be a helluva journey.

Its not first time when peoples try to live only for cryptos.
I am hear many bloggers try do it in Russia, but then do not tell how much they spent.
0.21 its big moneys for 21 days if compare with fiat moneys

This is a remarkable story but it highlights how bitcoin is really not ready to be used as a common means of payment. It would be easy to survive on the dollar equivalent of that BTC. I hope that in the future someone else can attempt this and have much more success. I think it would've been easy in a lot of cases to just attempt to explain to people how she can pay in btc and they can then convert that to fiat.