Is it possible to hack an iPhone 4 remotely using only a laptop?

Creep, and as long as here iPhone is not jailbroken it is not hacked.

Creep, HE cant hack or put any type of malware on it unless it is jailbroken.

There is a possible explanation for what he was doing. McDonalds hotspots are not secure. There is software available that can record the traffic going over the hotspot. If you record a few minutes worth of packets you can find the user IDs and passwords for the email accounts of anyone using the hotspot to check or send email if they have not set up SSL or TLS for their email accounts. Likewise for logging in to web sites. Just about all banks and other financial institutions require SSL to log in, but many smaller retail sites many not. So this is another source of data that can be used for identity theft.

Also go into the settings for her email account(s) and enable SSL or TLS if it is not already enabled. If it is she doesn't have to change her passwords.

Yes. The iPhone 4 - 6S on a firmware lower than 9.1 are vulnerable for remote exploitation that results into a complete take-over.

The exploit is possible on both non-jailbroken and jailbroken iPhones, but can only occur when airdrop is enabled to everyone.

The hacker can send a malicious image over the Airdrop protocol, which is then displayed on the lockscreen.

This image executes a script that installs a script that replaces the Phone.app with another malicious Application.

Because the Phone.app runs aa root, the hacker is able to start SSH and/or VNC connections to the iPhone.

From that point he can take over the entire filesystem and phone remotely.

Solution: Always update your phone to the latest firmware possible.