Though more seriously in a world where inbtgat isn't a word ('in that').
My cousin got married a few years ago and only I was invited (i have DH of many years and children). Thought 'hmmmm that's an unusual more' meaning the no partner invite (because face it is is unusual not to include family long term partners, it's even unusual with friend's partner when it comes to weddings).
I also knew that certain aunts and uncles and cousins werent invited (family argument involving the bride's father, it was his siblings and their adult children not invited)
Got to the (overseas for me) wedding and discovered I was in fact the only cousin there (the bride's siblings excluded they were there). My parents being the only other relatives on that side of the family. It was weird, there's twenty odd cousins. I am The Chosen One.
Might have been reasonable (some how) if on the other side of the family all cousins and their long term and short term partners hadn't of been invited but they were. Then the photographer called for an family photo with aunts and uncles - cue all lining up including the for a wet week partner of a cousin from the other side of the family and then my mum (sister of the father of the bride) was told 'not you'.
Now that's stubbing.
It was made all the more marvelous when said cousin that got married complained to me that she (and here siblings) hadn't been invited to another of our cousins wedding.
In a nutshell OP. It is what it is, if you can't go because of your DH being unable to care for your DC at night you can't go. Tell your cousin this, if she's annoyed by it she's daft.