This is a tough one man, but I've been in a similar situation to you. My last girlfriend had been with 9 or 10 guys, she was 21 as well. For me that's a high number.
But not only that I got her to come completely clean about her past. To my dismay I found out that she had been on an "f buddy" rotation with 3 different guys--as in effing buddy #1 one day, buddy #2 the next and so on.
I also found out that she had sucked off two guys at once, and on top of that had gotten an abortion.
This reeaaally bugged me but she seemed to try to balance it out by doing exactly what you're describing: spoiling me, bringing me lunch at work all the time, paying when we went out, being there at my beck and call. But her past was just too much for me to get over. I never completely trusted her because of her past, but then one day I came across an email between she and her ex. It wasn't too shady but she had previously told me that they weren't talking anymore and she didn't want to talk to any of her ex's now that I was in her life.
Oh yeah and her mom had cheated on her dad leading to a divorce. I know she's not her mom, but I believe stuff like that can be passed down. As sweet as she was and as much as she had "changed", there were just too many red flags for me, so I ended it. I don't regret it one bit, and that's what I would advise you to do too. There's just too many red flags there in my opinion man.