Hi @strongtogether,
@Afraser has pretty much covered the explanation. AC chemo is a very popular treatment and Doxirubicin is one of the most powerful chemo drugs available. If I remember correctly it is able to kill cancer cells no matter what stage of development they are at.
Rest assured that your onc would have prescribed the best treatment for the type and stage of the cancer. Googling can be confusing and bring up more questions than what you had at the beginning. I am sure your partner has been explained all the relevant information and passed that to you the best she can. Personally, I relayed the information to my husband and divulged only what I wanted him to know and nothing he didn't need to. I figured there was no point the both of us being worried constantly with the names of chemo drugs and possible side effects washing around in our brains. He gave the support I needed and I dealt with the rest. I found it easier that way, I never took him to chemo or appointments, that way there was only my emotions to deal with, I didn't see the point in worrying him anymore than needed.
Everbody is different in the way they handle these things. Maybe ask what she needs from you. She may be perfectly happy (if that's a word you can use in this situation) with the information and treatment she has been advised to have.
All the best with the rest of the roller coaster.