Wedding problems

I’m getting married next year and we’ve already started planning and have most things planned. The venue we’re getting married at is really nice and can fit 200 people. My mom. Grandma and my in laws are helping pay for everything and I’m so grateful! Trying to save as much money as possible we cut our guest list in half and some of my cousins I’m not even close with and live in other states aren’t invited since I don’t talk to them and didn’t grow up with them since they’re much older. Anyway we got our list and it’s just over 100 people with close friends and family and then my mother in law to be asked if she can invite all of her cousins and that she would pay for them. I don’t know her cousins and my fiancé just really knows of them. She said it’s about 25 extra people and that’s honestly a lot in my opinion and we didn’t really give her an answer but I really don’t want them there because I’m already freaking out about everyone watching me (I’m a bit awkward and shy) and then to add 25 extra people I don’t know into the mix scares me. I just want close family and friends and keep it on the smaller side. My fiancé isn’t even inviting all of his friends and my moms best friends aren’t even on the list because we agreed to save money because it’s $105 a person. Idk what to do because she did offer to pay for them and is helping us pay for the whole thing but it makes me uncomfortable all these people we don’t know there. In my opinion it’s our wedding and it should be our friends and stuff but we don’t know how to tell her no. Would we be awful people to tell her no? I just know we’re gonna also get stuck talking to all these people at the wedding knowing someone of our friends weren’t even invited. I really just wanna keep it small and 100 people is already a lot