D..
Put her diapers back on (not Pullups). When she has a tantrum, pick her up and deposit her in her room and shut the door. Don't let her know that you are outside of the door holding the doorknob. Let her think that you are nowhere around so that she does not have an audience for her tantrum. Only after she has stopped crying does she get to come out of her room.
Her behavior right now is at a critical juncture. You must deal with the tantrums and nip them in the bud. Potty training takes a second seat to this because you will NOT win here making her potty like you want. You CAN win the tantrum war.
NEVER give into her for ANYTHING when she has a tantrum. You cannot get her to listen when she is doing this. You just put her in her room and don't give her any attention whatsoever. When she stops crying, you open the door and say "Are you done?" If she starts up again, shut the door again. You must be firm and unapologetic. She will not want to be separated from you, but this is how you make her understand that she cannot do this without negative repercussions.
If she does it while you are out and about, strap her in her carseat and stand outside the car and ignore her. Stop whatever you are doing and just take her out to the car and all she can do is struggle in her carseat. be firm and tell her that if she has a tantrum, there is NO park and NO fun and you will take her home. Follow through every single time even though it messes up your fun too.
Get ahold of it now or you will be very sorry that you didn't. Once she understands that tantrums only get her dumped in her room or strapped in her carseat, she will straighten up and then you can readdress potty training.
Good luck,
Dawn