You lay out your proposal

"You want your legitimacy to be recognised and your state's independent to be protected,"

"I assure you that my legitimacy is unchallenged since I'm the only child,"

"And I'm sure there's some cousins five removed, and some bastards or twenty out there with some claim to your position," you hold up a hand to forestall the incoming protest, "it doesn't matter if their claims are legitimate or not. They can just replace you and then rationalize it later," You reconsider your thought, "You have done well to hold this trial as it prevents your enemies from doing so, but don't be mistaken that you can delay it forever without a permanent solution,"

"What is your solution?"

"First, there's the option of becoming a protectorate state,"

"Protectorate state?" Lady Eliza repeats.

"Yes. You submit your state under the protection of another country such as mine and in return you're granted certain level of autonomy. For example, my country will make use some of your army, but we will let you conduct your own diplomacy and economic activities, within reasons of course,"

"Within reasons?"

"It's pointless to have contradictory economic and diplomatic activities, right? Don't just think from your perspective. Imagine you're exporting wheat, and my country exporting wheat as well. If we're not careful, we will compete, and both will lose out. Rather than compete, it's more beneficial to cooperate,"

Lady Eliza nods. "Make sense. How about union of families?"

"Marriage? As much as you're beautiful and desirable, I'm not going to marry you,"

"Why?"

"Otherwise, it would be a situation where my kingdom absorbs yours and in return, I make you my queen,"

"Why not maintain the protectorate state status?"

"If you give birth to a son, the son will be the heir to my kingdom, not yours. You want to propose giving birth to two then? If that's the case, which one is which?"

"How about I give birth to a son which will be the heir to my land while you marry another one to produce the heir to your own?"

You give Lady Eliza a long, pointed look. "Why would I do something so troublesome just to satisfy your personal need to be independent of a man, and at the same time create the risk of a civil war?"

"What do you mean?"

"If I have heirs, one from you and one from another queen, then your son has as much right to my throne as the heir from the other queen. No laws or treaty will ever erase that fact. Just think, why do you think our son would be satisfied with yours when he can rule mine? Or even better yet, why shouldn't he rule both as a unified land? Instead of going through all this roundabout method, we might just as well get married and unify the lands,"

"So, you're suggesting that we get married?"

"I didn't say that. I'm just pointing out the second option is unifying the lands through marriage,"

"Any other options?"

"The third one is only normal trade relations where both of us buy and sell things to each other. We can agree on certain preferential status on certain items and services, but that's it. You choose your husband from those errand men, I choose mine, we don't interfere with each other's politics, at least officially,"

"Officially?"

"There's this proverb, 'keep your friends close, and your enemies closer'. You understand what it means, right?" You stand up and turn to walk toward the door.

"Where are you going?" Lady Eliza asks.

"You want more time to think, and I want to go have my lunch and rest," You stop halfway, "Please send Cynthia to my room,"