5 month old puppy won't stop jumping on other people

I've had my mixed breed puppy for almost 3 months now.

It's been... a ride taking care of her, but I've noticed she's slightly less absolutely crazy than she was last month. She rarely jumps on me and understands that she'll only get my attention when she's sitting. Specially when I leave the house and come back.

I live with my brother but it's mostly me and her during the entire day and she's chill, but the moment a visitor comes it's like she becomes an entirely different dog. She never attacked anyone but she is 30 pounds or so, so you can imagine what it's like for a dog that size that jump on you because she wants to play.

She doesn't bark at people but she gets overly excited and loses control of her reactions. She's been getting better at a lot of things (potty, obeying commands, etc), but with other people it's just been pretty much the same for those 3 months.

I've tried holding her until she comes down or keeping her on a leash until she comes down because that's what I read you should do and she'll settle down at first, but the minute I let her go she'll go crazy again.

I honestly don't know what else to do, every time someone comes here I have to put on an entire operation to either distract her (and the only thing that distracts her is food) or just keep her on a leash the entire time cause she simply won't calm down. It's virtually impossible to have a conversation with other people when she's in the room and not distracted by something she's eating. She'll jump on absolutely every single person except for me and she won't listen to me, it's like she gets so excited and stimulated that I just disappear and she doesn't listen to my commands.

And the thing is, I know some folks are cool with dogs jumping on them, but I don't want her to do that cause she'll definitely get bigger and some people are afraid of dogs too, and I wouldn't want to scare them.

So long story short my 30lbs 5 month old puppy gets incredibly excited when she sees other people and won't stop jumping on them. It breaks my heart because she's actually a super affectionate dog, but I just know folks will definitely be scared of her - and some, like my mother, already are.

What should I do?