HIV biting scare

My GF was attacked by someone on the street.  She bit him on the hand, and recalls tasting blood.  He then bit her on her hand, which also broke the skin (she was bleeding).  She also may have been scratched in the eye somehow.

We had protected sex at the 48 hour mark. She is on PEP at the 72 hour mark. Is PEP really necessary?  How risky is her exposure to HIV?  How risky is it to have sex or do anything else with her during this period of uncertainty (assuming a condom is used).

I understand that the man may not have even had HIV, and even if he did he may not have given it to her.  But why on earth would the infectious disease specialists give her PEP?  I feel like abstinence (on my part)  is no more crazy than her going on PEP in this situation.

[FredDu]

She also may have had the beginnings of 2 serious canker sores under her lips when the incident occurred.  She definitely had the canker sores 2 days later.

[joggen]

HIV is not transmitted through biting.

[FredDu]

How about swallowing blood when there are canker sores? Usually a non-infected person is bitten.  She bit him.  

[joggen]

No risk.