Anything can happen in a month. I wouldn't think about it too much. It's just a gathering to celebrate the upcoming birth of a baby. If go, take a gift and mingle with the men and be sure to make a point of talking to your son's girlfriend for just a bit. Nothing says you have to stay the entire time. If you feel uncomfortable, make your excuses after a bit and leave. It will be okay. No one wants to make a scene at a baby shower.
If her family speaks to you, be courteous and speak to them. Again, you do not have to go into lengthy conversations w/them.
Try to remember that this is an event for your son and his girlfriend. If they didn't want you there, you would not have been invited.
It will be okay. No one wants to make a scene at a baby shower.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.