What's the word for someone who knows what you need in advance?

Solution 1:

I'd say they are proactive.

proactive

adjective
acting in anticipation of future problems, needs, or changes

// Once patients have the big data about their bodies, the thinking goes, they can be proactive about their health, cut care costs and foster better relationships with their doctors.

[Merriam Webster]

Or forward-thinking.

forward-thinking

adjective
thinking about and planning for the future, not just the present:

• Forward-thinking architects focus on the long-term environmental impact of their buildings.
• The City has consistently shown an innovative and forward-thinking approach to providing services.

[Cambridge English Dictionary]

Solution 2:

She could be described as prescient:

a.1. Having knowledge of coming events; foreseeing; conscious beforehand.