Macs are the norm in the music industry because of latency. It is darn annoying to pluck a note then hear it after a quarter of a second delay. Apple became more serious about reducing delays between the input interface to producing the note, either through phones or speaker far earlier than Microsoft.
Most that I know use a MacBook Pro with 8GB memory and a graphics processor to offload the main CPU. I don't since mine does not have a graphics processor, but I'm not recording and mixing multi-track arrangements (MacBook Pro, Retina, 15-inch, Mid 2015).
The other popular Mac used is the iMac. Never seen a Mac pro used so far.
I would recommend a MacBook Pro with 16GB, and 500GB SSD as the minimum. Reason is you can run Windows in a VM much easier than with 8GB, At 250GB SSD, it will be struggle to keep the VM files on the SSD and still have good free capacity.
If she is serious about composing, she'll need a backup drive. I use a Samsung external SSD with drive level encryption for backups.... small and portable, plus encrypted in case it gets lost or stolen.
If you want recommendations from gigging musicians that have graduated from music college, check out Adam Neely's youtube channel and send him a message. He recently purchased a new MacBook to replace his old one. He might have something in one of his Q&A episodes.