At 7 months it is highly likely that she is in heat. Usually the first signs are a blood tinged discharge and swelling of her vulva. There may be changes in appetite, pattern of eliminations and mood. The entire period lasts approximately 3 weeks. The duration and intensity are variable especially with the first heat. The discharge will progress from bloody to "ice tea" colored to straw colored if the heat proceeds routinely. The only steps you need to take is to guarantee no exposure to male dogs. Be prepared to deal with the mess of the discharge and slight changes in habits, some people find using "doggy diapers" helpful. Please take a look at the video on spaying and neutereing.