Is my friend's behavior normal or overprotective?

I'm 29 and my friend "C" is the same age. We met in 6th grade and were good friends in high school. We became close again a year ago when she started dating my other best friend's brother. She has a good heart and she's fun to hang out with, but at times she gets a little bit pushy/overbearing.

In June 2020 I started dating an awesome guy whom I'll call "L." Initially C was very supportive and happy for me. One night her and our other friend "A" invited me and L over for a get-together at A's house. It was going good until C started asking random personal questions like "have you been to jail?" and "are you up to date on your child support?" He told her how rude that is and she got all defensive. She then turned to me and shouted "Don't let him take advantage of you!" even though there was no evidence that he was taking advantage of me (he asks me to get things from the store here and there, but he's done favors for me too so it's equal give and take). Everybody was on better terms soon after that but I was wary of having everybody in the same place again for a while.

Just recently I opened up to C about how me and L had been having some arguments. Nothing horrendous, he doesn't hit me or threaten violence. But he has used alcohol to cope when he has a lot on his mind, then took his frustrations out on me. I take responsibility for some of our problems; at times I have been too quick to emotionally react. When I told C about this she hit the roof and started yelling at me about how the relationship is "toxic" and "manipulative." She thinks I need to find someone more "age appropriate" (he's 43, I don't think age matters because we're both consenting adults). Me and L haven't fought lately but he seemed miffed that day when I was running behind (I was supposed to take him to work). Later that night he reassured me that he's not mad at me and called C and A on video chat to assure them that he would never try to ruin our friendship. C freaked out and screamed "YOU'RE A MANIPULATIVE PIECE OF S*** AND YOU'RE TAKING ADVANTAGE OF A DISABLED ADULT! PAY YOUR CHILD SUPPORT YOU ALCOHOLIC A**HOLE!" I am diagnosed as autistic but I've overcome a lot of my symptoms, plus he's been very non-judgmental and told me that he'd never let anyone make me feel like less of a person. Also before anyone asks, he is on time with paying child support for both his kids every month. The next morning C apologized to me, however as far as I know she hasn't apologized to L.

I know my relationship hasn't always been perfect, but as long as I'm not being abused I don't think anyone else has any say in it. I feel like C has projected her own problems onto me; her ex boyfriend is a drug addict and more or less ignored her throughout their relationship unless he wanted money. I appreciate her caring about me, it has just gotten to be a bit much. Any thoughts/advice are appreciated.

TL;DR: Friend has intervened in my relationship and assumed I was being abused/taken advantage of despite lack of evidence.