Your problem is very easy to solve. First,moving might not be the best solution but you might have to result to it if all else fails. If you have stayed in that house for a while,the rent you are paying is probably lower than the current market price - maybe by as much as 30%! Also,probably the location of the house - it might not be easy to get an equivalent if you are searching in a hurry.
My suggestion. Take leave - at least two weeks - throw her stuff out of the house (hire a watchman for the night as someone suggested) change the lock and padlocks,lock the house and go for a holiday somewhere remote - or even your shagz and be sure to switch off your mobile! Also,before you leave,inform the care taker or whoever that nobody should be allowed into your house lest he gets some people to break in! Or you can get a no-joke sister or cousin to 'house sit' while you are away! Another option is to have the watchie stationed there for a week (you can even have one for day and one for evening) to make sure she does not break in. At 'kazi kwa vijana' rates,this should cost you only 5K.
Never count on making a good sale. Have the purchase price be so attractive that even a mediocre sale gives good returns.