The best way to make a semi-sweet strawberry wine is to ferment the wine to dry, .990 and back sweeten to your preferred sweetness with a simple syrup (2 parts sugar to 1 part water, but you can make 3 or 4 to 1 as well).
You'll need a hydrometer to take the starting gravity level and to know when your wine is finished fermenting.
Once it has finished fermenting, rack into a clean carboy adding Potassium Metabisulfite (Meta) that has been diluted.
I highly recommend letting it age at least 6 months, during that time the wine will clear as the lees\sediment drop, you may need to rack the wine off the lees\sediment a couple of times.
After the wine has aged approx 6 months, fine\clarify it and filter it for that beautiful polished look (filtering isn't necessary).
Rack again.
At this point you'll need to stabilize your wine with Potassium Sorbate (Sorbate) and Potassium Metabisulfite (Meta) and mix gently so it stays in suspension.
Depending on the volume of wine, you can start to back sweeten by adding a half cup of simple syrup, mixing into the wine real well and tasting a small sample of the wine after 15 mins.
I'll continue to add the simple syrup until I reach the level of sweetness that we enjoy, I highly recommend that you let your wife taste every sample as well, it's very important that she likes the wine, my wife is my taste tester.
This is a real easy wine to make and real easy to back sweeten, just remember, you'll want to stop adding the simple syrup when it is almost to the level that you would like, the syrup will actually continue to integrate into the wine.
I hope that this helps, if you have any questions don't hesitate to ask.