Hmmmm.......she's talking about setting up two households, but hasn't discussed it with you? I think you probably need to raise it with her and have the conversation because I assume this is on the back of the letter, and the whole point of that was to trigger some communication between the two of you rather than between W and S20 (BTW, I think she's totally out of order if she's trying to use his money to leave).
Hope you're having a good day- I feel like I haven't spoken to you for AGES!!