If Paris is already her dream, I’d honestly lean toward doing a land trip based around Paris rather than a cruise.
Cruises can be fun, but they’re usually better for people who want to see many places briefly rather than really experience one place.
A few things to think about.
Why a land trip might be better
You can slow down and actually enjoy Paris instead of rushing through it in one day.
Easy day trips from Paris: Versailles, Champagne region, Loire Valley castles, Normandy, Bruges, etc.
Much more flexibility with your schedule.
Hotels in Europe often feel more spacious than cruise cabins.
A really nice anniversary itinerary could look like:
4–5 nights in Paris
Eiffel Tower, Louvre, Seine river walk, Montmartre, great cafés.
1 day at Versailles
2–3 nights somewhere else nearby
Options:
Champagne region (Reims / Épernay)
Loire Valley castles
Normandy coast
Bruges in Belgium
You get the romance of Paris but still see more of Europe.
What a European cruise is like
Pros:
You unpack once
You see multiple countries
Meals and logistics are easy
Cons:
Very short port stops (often 6–8 hours)
Big crowds getting on/off the ship
You usually see only one small part of each city
Cruise cabins are indeed pretty small
Also, if Paris is the main goal, most cruises don’t actually go to Paris. They usually stop at Le Havre, which is 2.5–3 hours away.
A good compromise
Some couples do this:
5 days in Paris
Then a Mediterranean cruise (Italy, Spain, Greece)
That way she gets both experiences.
Great resources to start planning
Rick Steves Europe (YouTube + website)
Wolters World (YouTube)
The Endless Adventure (YouTube)
Rick Steves travel guides for Paris and France
They’re excellent for understanding what travel in Europe is actually like.
If it’s a 25th anniversary once-in-a-lifetime trip, my personal take:
Spend real time in Paris and a couple nearby places.
You’ll remember the cafés, walks along the Seine, and little moments far more than rushing through cruise ports.