I don't know about specific laws in Florida, but where I am at, I do not believe she'd need an ID, if JE as an adult male was buying cigarettes or alcohol. As far as I know if an adult comes in and wants to buy cigarettes or alcohol the clerk doesn't have to make sure everyone who is with that adult is also an adult. If someone looking like he or she could be a minor came in by him or herself wanting to buy cigarettes or alcohol only then an ID would be required.
I'm a barteder at a club in Florida, but I used to work at a gas station quite a few years ago. Here, we have a meeting every three months with the woman who handles our liquor license... she works hand and hand with ATF (Alcohol, Tobacco, Firearms) who makes sure she knows about any laws that have changed... actually any changes in anything that could be used against us.
In Florida, if someone looks 27 or younger, you have to ID them for cigarettes. If someone looks 30 or younger, you have to ID them for alcohol.
As for the "group" situation... Let's say I am working at a gas station... a group of young people come in and head back to the coolers (It's my job to be paying attention) and only one of them come up to the counter to pay for a case of beer... the rest of them just stand back... By law, I have to ID every single one of them. Even if they leave the store... they had been in my store, helped pick out the beer, etc... No beer for you!
Personally, seeing pictures of JE, I would ID him for alcohol. He looks under 30 to me. Let's say that I'm behind the bar at my club and JE walks in... and an undercover ATF Agent is sitting at my bar (watching EVERY.THING.I.DO!) and I don't ID him... if the Agent thinks that JE should have been ID'ed... he will stand up and flash his badge... ask to see JE's ID himself... if JE doesn't have any identification on him... guess what happens? Yes, I am given a citation. It doesn't matter if he is prove to be over 30... I would have to go to court (pay court costs)... after going to court, they would most likely not make me pay a fine because he is over 30... but if he wasn't over 30... I would have a FINE. One that I really can't afford. If I served anything to a minor (cigarettes or alcohol) I would be arrested ON.THE.SPOT. and after a hefty bond, legal fees, court costs, and fines ($5,000 PLUS) I would also not be able to sell cigarettes (3 YEARS) or alcohol (7 YEARS) in the State of Florida.
On the other hand, Britney, to me, looks at least 16. You better bet your butt I would ID her. If JE walked into my store (club) and asked for two different brands (cigarettes or alcohol)... I would ID Britney too. By law, I am responsible for who I sell those products to. JE would get charged with "providing" to a minor... I would get charged with "selling" to a minor. Quite different charges.
Maybe Florida Law is stricter than other places... I'm just trying to explain how this cashier could know that Britney had a fake ID. I can tell you this though, Britney wouldn't have gotten a Fake ID over on me... I can tell a Fake ID quick!