I can't provide an exact answer. I think that all depends on how well that person can type Simplified Chinese - since Pinyin input is the most popular input method for Simplified Chinese currently.
In my experience, if your friends always response in traditional Chinese, and she's like 30+ years old, I am sure she's probably not good at Pinyin/Unwilling to use Pinyin.
BTW, no matter she uses Pinyin or Bopomofo, that's only the ways of typing. That won't affect the communication as long as you know both Simplified/Tradition Chinese. But if you need phonetics to learn, you may have difficulty. At that case, you'd better leverage the online Dictionary tool like yellowbridge.com or even YouTube.
Learning phonetics or pronunciation with Bopomofo seems less efficient to me since all modern Chinese dictionaries provide pronunciation in Pingyin in general.
From a blog post, we can tell even in Taiwan, people start teaching Pinyin over Bopomofo. According to her view, Pinyin is more friendly to a new learner.
If you learn Simplified Chinese, I would definitely recommend Pinyin. I tried to learn Bopomofo myself but I found it difficult. From my point of view, the language itself should be a tool, not a purpose.(Unless you have an academic study purpose)