Partner moving to US for marriage, ask for L1

My partner works at a product company that has a US HQ quite close to where I live and work. She is what you would call a critical resource of the company leading and driving multiple projects. She likes her role and while she will be relocating to US, wants to do everything to keep it in one way or another.

Besides from the usual process of submitting resignation, how can she make effective use of the fact that she could potentially move here internally on an L1 visa or worst case keep connections warm and re-apply for a role here after relocating to US. Anything better than notice period and severing all ties.

My perception of moving internally to US/Europe has been that its not only extremely difficult because companies here would prefer having an India cost center given its layoff/recession season in US but also due to the challenge of headcount requirements in the same business unit. Besides an L1 application costs about $15k.

All of these factors make things trickier for her to keep her job in some form or the other.

How should she make the most of this situation? Are there any other outcomes here that I am missing?