If I understand your question:
A) You want to connect your RPi to MacBook.
B) You have a running RPi-3, I assume, originally connected to a friend Wi-Fi.
C) You don't have your home's Wi-Fi password, however I assume the MacBook is Wi-Fi connected.
C) No physical access to the Access Point and no access to switch to provide eth0 access.
So, you want to connect to your Wi-Fi without using the WPS auto configure button.
Your options are limited. Your best solution is to find the Wi-Fi password.
In a Windows box connected to the subject Wi-Fi , open a command prompt and then:
netsh wlan show profile key=clear name="xxxx"
This will show all the past Wi-Fi connection plain text passwords ... no more secrets.
If you mac have Ethernet connectivity, perhaps you can share the Wi-Fi doing Internet Connection Sharing and just plug your RPi to the Ethernet port.
pd: If you know the SSID and password of your home Access Point (router), you can add as additional network statement on
/etc/wpa_supplicant/wpa_supplicant.conf keeping your friend's definition.
ssid="YOUR SSID here"
psk="YOUR PASSWORD HERE"
id_str="YOUR COMPUTER ID HERE"