I had contacted sexually with my Girl friend on 29...

Is your partner pregnant ?
no , she is not , getting period confirm not being pregnant  from the sexual intercoruses between the previous and current period 
What is the possible cause of your partner medical condition ?
PCOS can lead to hormonal imbalance which delays period . but its possible to be caused by other medical conditions such as : 
1. malnutrition and low weight 
2. Hormonal changes 
3. Some medications such as Medroxyprogesterone acetate
4. stress
5. Obesity
6. Thyroid diseases
7. gastic system disease (wheat allergy)
What is the treatment of delayed period :
1. avoid stress  and have plenty of rest 
2. healthy life style including health diet and regular exercise 
3. consult GYN doctor to do the needed routine medical test and determine the treatment pathways ( if needed ) 
4. in case of hormonal changes , doctor may prescribe medication to correct hormones imbalance such as duphaston , which you should take a pill every 12 hours for 5 days  
5. in case of thriod hormone abnormalties ( usually accompanied with other symtpoms ) , doctor will prescribe medication such as Levothyroxine
6. in case of other chronic disease such as ovarian cyst ( PCOS ) or other disease , doctor may need addvanced examnation to determine the causes and treatment pathway 
Needed medical examnation :
1. physical examnation 
2. Pregnancy test 
3. vaginal culture and urine test
4. productive system ultra sound 
5. hormone levels including productive system hormones and thyroid hormones