I do that...and then I run out of grapes. It has to do with trying to do everything at once, probably. Even when I'm fighting the entire French navy, I still tend to have stuff like 4000cwt of mahogany in the hold.
Bring more grapeshot. Or, if you've just captured a French warship and are now low on grapeshot, transfer that mahogany onto the new prize and take all its grapeshot for yourself.
Having said that, you won't throw much grapeshot at the
Dauphin Royal in the climactic battle near the end of the story. You do not want to trade broadsides with that monster because while you're sending grape at her, 52 cannonballs are coming the other way.
The Moorish sabre is good enough for slicing the enemy but not so good for blocking the enemy from doing it to you - its piercing and blocking are little better than a basic swept-hilt rapier. Once you start finding them either in stores or on dead enemies, give Lucia a Hibernian, or for preference a Knights Templar sword or a Polish szabla.
Or download this and copy it into place.
If you change your mind, just talk about boarding again...
Regardless of what you've told her, Lucia
will join you when you're boarding Piers Downing's convoy. This is probably why she joined you and definitely what she's been looking forward to, and she will not be left out of the action. (But she does remember what you told her and will revert to missing or joining boardings accordingly, after the convoy battle.)