No, I don't. To begin with, if the partner had a terminal illness, then she would have resigned herself to losing him a long time ago, so she would have started the grieving process already. Secondly, as you say, there is no set time - some people need years of being on their own before moving on, but others are ready to move on in a matter or months or even weeks; we're all very different. Thirdly, the word 'boyfriend' can mean different things to different people - he may be the new love of her life, or he may just be a friendly shoulder to cry on.
Poor lady, she's been through a dreadful time - she needs good friends around her at the moment, so just try to give her all the support you can and don't worry about the new boyfriend. xx