This offer released in the media is quite old. Navratilova said that she would love to help Petra somehow, but then Petra said that Martina hasn't spoken to her.
I think that Martina should offer her advises to Petra in person, not through the media.
Until then, it looks like Martina just wants to make alibi, that she has done everything she possibly could.
Nevertheless, I think Petra should find Martine on her own and ask her for advises because she is the one who is struggling and needs to find a way out of this slump, she should be trying to find every possible person that could help her. But probably she just don't want to yet.
One of her disadvantages/advantages is her stubbornness. Her strong head helped her keep believing even when she was making errors and winning matches in tight three setters, but her self belief was high enough to get her out of this and she could start to play for winner again because she got through. This is attribute of the true champions, but it can also be bad for them when they are making mistakes and don't want to realize it.
This is also the reason why she is capable of losing matches where she just keeps making errors while trying to hit winners again instead of changing strategy. The only thing she can do about this is to learn how to tell apart the situation if she should keep her aggressive strategy, survive the short slump and start to hit winner again or if she should just change her game plan for a while and go for plan B or C to avoid losing the match.