File only once the services agreement is signed and the two companies’ relationship is documented; the customer site needs to be identified in the petition, so its readiness sets the earliest filing date. Allow the current USCIS processing time, or premium processing, before her first day.
The contract, the petition and the installation form one sequence
The offsite analysis depends on the actual agreement, so the petition cannot be drafted honestly until the customer contract is signed and names the site, the deliverable and the control terms. Get that signed first. In parallel, gather the payroll evidence for her continuous year and the corporate registers for both entities, because those do not depend on the customer.
Once filed, the initial approval can be for up to three years, and an eighteen-month installation fits comfortably, but build in time for an approval to arrive: check current processing times, and decide whether the customer’s schedule justifies premium processing. She should not begin work at the yard on a visitor entry while waiting. If the installation slips and a second customer is added later, the offsite analysis must be repeated for that site.
Keep the five-year L-1B maximum in view when agreeing to follow-on projects, and track both companies’ active-business status throughout, since either ceasing operations ends the eligibility.