Well, according to the will of Jean 1er (1454) L-H would be ineligible for the Monegasque throne if she married him. Two options, therefore, present themselves: either L-H marries someone more amenable, or Monaco goes to a younger line. The only other suggested husband that I can find was the "Chevalier Grimaldi d'Antibes". After some initial confusion, I realised that this wasn't her bastard half-brother

However, I don't know exactly which member of the Antibes branch is meant, but OTOH, there's only one with the right sort of birth date: Honore IV d'Antibes (1701-1743). I thought 'Chevalier' implied illegitimacy, but there were several members of the Guise family who were legitimate Chevaliers, and I can't find any Antibes bastards, so I'm giving Honore he benefit of the doubt. I suppose other French noblemen would have been considered if Goyon de Matignon had been difficult about the whole thing out of... pride, I guess? I'm pretty sure he only married her for the cash in any case.
If the marriage had gone ahead, the next heir would be L-H's sister, Marguerite Camille, who married Louis de Gand de Merode de Montmorency (and he might have changed his name to Grimaldi if it meant a chateau on the Riviera) but she seems to have been unable to bear children (Louis had short-lived kids with his first two wives) which leaves us in a difficult position when Marguerite dies in about 1758. The next heir would be a descendant of Hercule, Marquis des Baux (died 1651) but they wouldn't have the Grimaldi name and I'm not sure whether a descendant of a female Grimaldi can put himself in the line of succession by adopting the name post facto. If these descendants were allowed, the heir would be Michele Imperiali, 7th Prince of Francavilla (1719-1782) and he would presumably lead Monaco towards the Sicilian/Spanish orbit (OTL he lived in Naples after 1755). If not, Monaco would go to the nearest Grimaldi heir: Sauveur-Gaspard Grimaldi d'Antibes, son of Honore, the guy I think was the Chevalier Grimaldi d'Antibes.
So basically, the Antibes branch becomes much more likely to inherit Monaco, and if not, all the nobles of France will fight over the Grimaldi heiresses. Francavilla is basically a dark horse.