The important point is, her card may say "Valid Only With DHS Authorization". And this is very limiting, as requires showing green card to employer.
If she has capacity to do it now, it's best to replace it now, because once she's going through I-751, many SSA officers won't cooperate with her asking to get unrestricted SS card. I-751 itself can take few years. So it would be very unfair to her to be in stress few years down the road when she wants to join the workforce again.
In my humble opinion, the more rights and freedoms immigrant has, the better it is for immigrant and their family. Updating SS card (if it has the writing) is free. Maybe it doesn't apply to her, I just want to make sure you have a smooth ride.
Of course, you know what's best for your family. Good luck!