I am so sorry to hear of your loved one's passing. My deepest condolences to you and your family. Seeing that card must have been a bit of a shock too.
The Ace of Spades is the equivalent of the Ace of Swords in tarot. All Aces are positive cards. They represent the pure energy of their suit. In this case that is the energy of clear vision, clear thinking and clear communication. Sometimes it will herald a breakthrough in understanding, a new idea, or a sudden realization of the truth.
I think the card is a message of reassurance. That your partner has reached a better place. If they were in pain, then know it's gone. If they had trouble with communication, then know all is well. And keep looking out for more signs.