Many women have reasonably easy bruising. If this is a new issue, she should discuss it with her doctor. But there definitely is no reason to suspect HIV. It's not an HIV symptom. And your exposure 3 years ago was virtually zero risk. Since you're nervous, you should have an HIV test to prove to yourself you aren't infected. Assuming you are not otherwise at risk for HIV, you can be sure of a negative result.
Regards-- HHH, MD
I would like to add that these small bruises dissapear after few days, infrequent, and not same location
That is an excellent description of garden variety, harmless easy bruising.