Kertrats, I see you HAVE declined! - well done. You've reminded me of one of my best pals, who had an ... entertainingly demanding neighbour.
She moved into his very rural hamlet & immediately set about Queen Beeing, installing ugly gabions & a very loud hot tub, & having interminable noisy outdoor weekend gatherings, which she tried to insist my pal attend. He could not move outside his front door without being hailed & an attempt to pull him into her house for a drinking session - intrusive, thick-skinned, you get the picture.
She was getting married, & insisted my pal attend that too - in a city maybe 100 miles away. Pal is made of stern stuff, & refused all advances, as she was a coercive nightmare of biblical proportions bit bossy.
The wedding fell through, as she broke up with that b/f. Woe!
The very next weekend, she had a new b/f in tow.
She barged over to my pal's gaff & insisted on introducing them.
It emerged that she was now marrying THIS b/f instead - &, get this, it was great because he was the same size as previous b/f, so would be wearing the same suit she'd ordered for previous man.
The wedding was to take place on the same time/date, at the same venue.
In other words, she was hellbent on her wedding, & the small feature of supplying a groom was NOT going to be a problem for her.
She then took to knocking at my friend's door, again to insist that he attend her wedding. He had a great excuse - it was the weekend of his 50th birthday, & he had his own large family attending his party.
Not a problem as far as this neighbour was concerned. My pal "just" needed to cancel his venue, & pay for a coach to take his family & pals to HER wedding venue instead.
He did not comply, but dined out on her batshittery for years.
I all hope this makes you feel a little better about your cousin's odd choice of venue 😁