Does sertraline 50mg cause sleepiness and cause a women to loose sexual desire?

Yes it is possible: Sertraline is an ssri. It has the potential to cause drowsiness (she could take it at night) and ssris can interfere with one's sex drive.

It can: Sertraline - as with other ssri medications - can cause decreased libido and/or anorgasmia. In many cases it has a stimulating property, but some patients may experience sleepiness instead. If the latter should occur, taking the dose in the evening might decrease any daytime sleepiness.