As I understand it, her finances aren't really the reason she'd be eligible for legal aid. The only family cases eligible for legal aid are where DV has been accused (which is why so many exes accuse Dv - free lawyers and they don't need much in the way of evidence - a letter from womens aid possibly, who just believe what she tells them). I may be wrong but if she is eligible because she claims to be a victim of DV I don't think her finances are looked at at all.
But no don't raise it - focus on your case. It could be useful evidence for later though - if you want to prove she's lied about something. But it needs to very clearly prove she's lied. Not guesswork or assumption. If you're separated, you won't actually know what her bank statements say. And as mentioned above it could be seen as controlling behaviour - talking about her finances. There are tricky lines. I know cases where a Dad has asked the court to order the Mother producing her medical records. For very valid reasons! And the court sees this of intrusive of the Mother's privacy and the Dad being a bit controlling.