Well, I have to say you surprised me! This might be the first time I have heard of a "twist" that might actually make a difference. This assumes, of course, that yours is a straight story: that's the first I have ever heard of using breast milk in a sexual context. And it seems improbable that a woman would know that she is positive, recently infected, knows her viral load to be high, and also has the insight to know to tell you that particular sexual practices are safe. Even if you are being truthful, I have to wonder whether your partner is.
You are correct that exposure to breast milk is not generally high risk, because HIV viral load is low in milk and not highly infectious (same as sweat and saliva--and both mammary and salivary glands are biologically very similar to sweat glands). However, to my knowledge there are no data specifically about HIV viral load in milk during a woman's initial HIV infection. You also are right in your apparent understanding that hand-genital contact isn't a risk.
Despite the uncertainties about the effect of your partner's supposed new HIV infection, I consider your risk too low to worry about and see no clear need for an HIV test. But most people nervous enough to ask the question, and in particular to come to this forum and spend $15.00, are not be able to relax based only on my reassurance. If that applies to you, it's fine with me if you get tested.
Note the forum rule about a maximum of 2 MedHelp questions in a 6 month period.
HHH, MD