there baby regenerated into mels who in turn became there best friend and she in turn regenerated into River Song....in other words wibbly wobbley timey whimey
In that universe yes but a real mum wouldnt
A real mother would stop looking for her child once she found the child. Amy has found her child (River). She couldn't go back in River's timeline to find her without harming (probably destroying) River. How Amy feels about what was done to River is clearly shown in the scene in the pyramid, just before the wedding, where Amy speaks to Kovarian about never being able to see her baby again, then presses the eye drive back into Kovarian's eye to ensure that Kovarian will die -- painfully!
Unfortunately, it's really the kind of dramatic situation that Doctor Who is not built to handle. I can say from experiece that a parent who lost a child and knew someone with a Time Machine wouldn't give a crap about the space/time continuum. In fact, if you look at "The Wedding of River Song", it states that River is willing to go much farther for the Doctor than Amy is for her baby.