I get it and I feel for you. I wouldn't be happy about it either, if my new SIL showed up an hour late for my wedding reception, which also messed up the photo session, and also only brought a card. That's a deluxe package of rudeness.
I wouldn't say anything though or ask my husband to. She's already stated why she was late so all that would be left to say is "Where's my present?" Which would be funny and she probably deserves it but I don't think it would make you and your new husband look very good lol!
Also, it could be that she left the gift at home, ordered something that didn't arrive on time or meant to put a gift card in with the wedding card. In other words, it could always be a mistake or your gift could still arrive.
But as we see here, people often see things very differently. So while you obviously consider a wedding reception that's separate from the wedding that most of the guests weren't invited to is every bit as valid as a reception immediately following the wedding, with everyone invited to both. However, many other people don't view it that way at all. They might feel dismissed to not have been invited to the wedding or they might truly consider it somewhere in between a party and a true wedding reception.
The sister trying to sell her house is apparently very important to her. All around, I could see her truly not knowing she's done anything that anyone would take offense at.
Also, sometimes there's weird jealousy among siblings. It's also possible a slight was intended but that it wasn't directed at you. Maybe she feels like her parents favor her brother and she's not considered important enough in their family. Or her life might not be going very well and she's taking a little swipe at you and your husbandn's happiness.
Or she could just be a rather self-centered and thoughtless person.
Anyway, I think the best course of action at this point is to just keep an eye on her. I wouldn't doubt if you'll get a more full understanding of what this was all about in time.
More importantly, best wishes with your new marriage!