advice needed for inlaws

My LO is 3 weeks old and we just went to our first Sunday dinner at the inlaws.

My MIL invited her extended family without telling me or my husband so we were overwhelmed when people kept showing up to see the baby. I suffer from anxiety and as a FTM letting people handle my baby has been a struggle. I usually limit visitors to smaller groups to avoid any anxiety attacks (no more than 5 people).

Everything was going ok until my husband's aunt grabbed my baby from my SIL arms and started kissing and touching his face without washing her hands (we have been telling people to wash their hands and no kissing the baby). To add to the problem, she reeked of cigarettes and alcohol and almost fell when she went to sit on the couch. Once he was back in my arms I started nursing him and intentionally let him stay there for 20 minutes because I didn't want him to go back to this aunt. The aunt literally sat next to me the entire time asking if she could burp him and commenting on how I was taking too long. I did my best to ignore her but could feel my anxiety rising.. with more badgering from the aunt and a screaming baby I ended up having an anxiety attack and breaking down crying.

My husband was not in the room this entire time so he wasn't there to say something on my behalf.

I am not a confrontational person but I definitely would like some advice on how to handle situations like this in the future. I have a feeling this won't be the last time I'm in an uncomfortable situation regarding my child and i would like to be better prepared for next time.