If you already have the $50 Tracfone and you get okay coverage with that, I would not give up on it just yet.
First, there are always all kinds of codes for tracfone minutes. Never add a card without an internet search to see what the deals are. Tracfone will also call and email you about deals. You could probably double or triple the minutes with a code vs retail price.
BTW, did you get the double minutes for life card with her phone? If not, you absolutely want to make sure you have this...buy it and add it.
Another option is with Tracfone are the monthly plans. This is fairly new (last year or so) but worth checking out on their website. You will still get double minutes with the plans.
Also, maybe do some research on using your Tracfone. You can receive partial texts for free (they come in and you can read the first 10 letters or so without actually pressing okay to get the text and pay for the text). If your daughter can manipulate this enough with her friends, that will save her a ton of minutes.
We have two teens (14 and 15) and they both have tracfones. They both have their Facebook accounts hooked to their phones. Our 15 year old is especially fierce with texting, but he has learned to live within his budget of minutes or he runs out for the month and has to go without. I think this is an absolutely vital lesson for kids. Use this as a teaching tool now and it will translate to finances and budgets in the future.