Work backwards from the season, not forwards from today. If a credential gap has to be closed by study, that alone can take two or three terms, and the employer letter cannot be finalized until the start date and duties are settled. Applying into an unresolved schedule produces either a refusal or an authorization that no longer matches the job.
The long pole is the qualification, not the queue
For a straightforward Canadian applicant the application itself can be quick, which is why timing failures here almost never come from processing. They come from the preparatory steps. A hospitality certificate begun in September is not finished before a May opening.
An official transcript can take weeks to arrive. An employer that has not yet decided whether the role is general manager of one property or a regional position cannot produce the letter that describes it. Marguerite should therefore fix three things in order: the branch she will qualify under and what remains to be done for it, the exact duties and dates the Michigan group will commit to in writing, and only then the mechanism, whether that is presenting at a port of entry or waiting on an approved petition.
Two interim arrangements are worth refusing outright: starting the American work remotely from Ontario before any status exists, and travelling as a visitor to help open the season while performing productive work.