Her period ended then she saw some drops of blood

Praise be to Allah.

The blood which means that a woman should stop praying, fasting and having intercourse with her husband is the blood of menses. Allaah has given it signs which are well known to women. With regard to the colour, it is black; with regard to the smell, it has an unpleasant odour and is also thick. Anything other than that is not menstrual blood, rather it is the blood of istihaadah (non-menstrual vaginal bleeding). This is what women call nazeef (lit. bleeding), and this bleeding does not mean that a woman should stop praying, fasting and having intercourse with her husband. 

From the description of the blood and from the fact that it is so little, it seems that this is not menstrual blood, and based on that she has to pray and fast, and it is permissible for her husband – if she is married – to have intercourse with her. 

We have mentioned the differences between menstrual blood and the blood of istihaadah in the answer to question no. 5595. 

And Allaah knows best.