Any destination in the US, Canada or Caribbean that has water and scenic views she will be happy.

You might get better response if you re-post on the Air Travel board (see the 'change forum' pull down menu? )

If you have time get more miles

Just use your MileagePlus credit card to automatically pay your monthly bills, like ... MileagePlus Credit Cardmembers can redeem miles for any united.com flight with no ...
www.united.com/page/article/0%2C1360%2C1261%2C00.html

my wife and I both open FF CCs get the miles close the cards

get lots of miles rarely pay for air that way...

We did this with AA got 2 free Transatlantic Last

You will have to play around on United.com

there are several tiers book in advance as far as your can

In late Jan for 25000 miles each off season you can

go RT to beachy places in CA(San Diego) and Florida.

I would probably head for Miami South Beach

betterbidding.com for nice priceline hotel clayhostel.com

nice for budget there...

You need more miles to go elsewhere but if you can pay more

might look at maho.org St John USVI or stayhawaii.com

Kohala Coast princeresortshawaii.com my fav

Even Volcanoes NP there it is AWESOME.

Happy Planning!

I've been a Mileage Plus member for many years, and have taken several trips with FF miles. As far as your available options, please see the mileage reward chart. The miles they list are for one-way so you need to double them for round-trip:
http://www.united.com/ual/asset/United_Star_Chart_eff_after_6_15.pdf

My experience is that will have trouble getting FF tickets for Christmas week, one of the busiest times of the year. United doesn't offer very many seats on those flights (because they can easily sell them), and the ones they do offer tend to get scooped up pretty quickly.

AS you can see from the chart, destinations in mainland U.S. are only 25,000 miles R/T for an economy ticket. Mexico,Central America and the Caribbean are 35,000. Hawaii is 40,000. Maybe one of those would work. Good luck to you!