I have a chat friend from Nigeria with a British passport, who needs to travel to Dubai, however she is insisting in a law in Nigeria that states she has to carry on person 1000 USD before catching her flight as this is a guarantee that she will not be dependent on Dubai government for any issues. Is it true that she must have this money in person before traveling to Dubai?

This is clearly a scam. I'm assuming your chat friend asked you to procure that $1,000?

SCAM pure and simple.
A British passport holder is NOT curtailed by a dubious Nigerian (SCAM) Law

LMAO! No! It's not true. She's lying to you for money. She'll continue to lie in order to get more and more money from you, until you finally realize that it's a scam. She's doing the same thing to hundreds of other guys. Fact is, she's probably 50, fat, and not at all attractive. She may even be a he. This is her job, scamming people. You're just a possible victim.

It is not true, there is no such law, This is one of the largest and most well known scams,

It is used in various forms, normally in dating

https://www.askmehelpdesk.com/relationships/if-gorgous-chick-ghana-wants-money-romance-scams-read-677503.html

Substitute Nigeria, for Ghana.