To answer the question you have twice asked, I don't think that you can be 100% safe, except by going the abstinence route, or as someone suggested, a quick wank while you watch her in the shower or better yet, a slow wank as you have her and her friend put on a little Lesbo show for you.
But if you use the precautions that you have specified, then you will most likely be 99.99% safe, which means barring an act of God, you will not catch HIV. But strange and unexpected things can happen, and sometimes do. For instance, let's say a BG falls in love with you and wants to have your baby. As other BMs will tell you, this happens, and they can become very vocal about their desire to have your offspring. If, in such an instance, a girl was really devious(and I am not suggesting that any B G would do this), she might find your condoms in the drawer while you are in the shower, and with a very fine needle, poke a hole in each condom. I am not saying that this might ever happen, but just pointing out that, as much as you try to be 100% sure, there are strange and unexpected occurrences in life.
In life, one may think he is in control, but the truth is that you never really are. When things are going your way, it is almost impossble not to give in tho the seductive illusion that you are in control of your own destiny. But that is only an illusion, because the truth is that forces beyond our comprehension, what I simply call fate, is in the driver's seat. Look what happened to G's niece. Could have happened to any one of us!!!
JayBee