When Hall and Jagger started their relationship he was still married, actually. So she was “the other woman” for a while. And when they were dating he was seeing other women as well. This was widely publicised in the papers, so it’s pretty sure Hall knew about this as well. Later Hall herself said during interviews…

She was a millionaire herself when they split, so it’s not exactly like she went hungry after the “divorce”. People seem to overlook that tiny detail; she was a rich celebrity before she married Jagger. And by the way, they settled for $25 million.