Sell it without paying taxes then take your 140 gain and get you some multifamily deals that would cash flow better than the house would. good luck and congrats.  

Looks like her gain well exceeds that.

What are my best options to avoid capital gains tax?

Live in it long enough to qualify as a primary residence  then sell without having to pay capitol gains.

She has technically "moved back" to Sweden on the books and I've heard she may need to pay Swedish taxes on the capitol gains after sale of the condo.

buying a single family that's in good shape, may not require as much attention as a fourplex in a run down area. 

Goal in Real Estate and Stocks/Bonds is CashFlow & Capital Gains.

The cash is earning 5% -6% in rewards checking accounts and that really offsets the gains on the small debt relief.

Go street by street, recording and photographing anything that looks interesting to you: abandoned properties, fsbos, ongoing rehabs, and anything else that gets your attention and that might put you in touch with a motivated seller or buyer.

Hey everyone . . . it has again come to my attention that the site's email notification system for discussions has not been fixed, as I had thought.