Thank you, Teacher 8. I'm 99.9% sure her I-485 receipt notice was included in this renewal application. If USCIS asks for proof of "application for adjustment of status", it would mean I-485 notice; however the RFE is asking for "underlying immigrant petition associated with your application for adjustment of status", and it gave a few examples (I-140 etc.), it seems they are asking for something other than I-485.
I'm not sure if my reasoning makes sense. I'm now planning to send receipt notice for her I-485, my I-485 and my I-140. If you think of any other suggestions, appreciate if you could let me know.