ProtonVPN on corporate WiFi network

Hi All. Hoping you can help me with this question and solve a debate between me and my best friend.

She works at a major corporation that has high-level IT security. She has proton VPN and wants to use it on her personal iPad while at work.

In order to access Wi-Fi while in her office, she has to use the corporate Wi-Fi network. In order to access the corporate Wi-Fi network, she must enter in her employee number and active directory password, accept the terms and conditions, and then she is on the corp network.

The question that I hope you can help us answer is if she is connected to the corporate Wi-Fi and uses proton VPN, can the company only see that she is using proton VPN or are they also able to to see her specific web traffic and activity? Or asked differently, what can the company see related to her being logged on to corporate WiFi while running proton vpn? Thanks so much!!