It's very likely you will be able to hear the baby's heartbeat with a doppler at almost 12 weeks.
Since you've already discussed your medical history with her, at the first appt you might have some paperwork to sign but other than that it should be like any other routine prenatal appointment. With my midwives at the free standing birth center I go to, the appointments generally include:
* peeing in a cup to check for the presence of protein and glucose (which I do myself in the bathroom and tell the midwife what the results are)
* getting weight/blood pressure/pulse checked
* midwife asks if I have been having any unusual symptoms (weird headaches, swelling, etc)
* midwife discusses any questions I might have
* listen to the baby's heartbeat with a doppler and get the heart rate
* measure the fundal height (at 12 weeks, it should only be about 3 fingerwidths above your pubic bone so she might not even try to measure it yet - I don't think mine actually uses a tape measure to measure centimeters until 18 or 20 weeks or so) - but since she's never seen you before, she'll probably palpate your uterus a bit to see if it feels about the right size for your dates
I don't know how much besides medical history you've already talked with her about, so she might go over things like appropriate nutrition, warning signs to watch out for, and what expectations/wants you have for the birth. Midwives usually spend a pretty good amount of time with you at prenatal visits. It's a good idea to write down any questions you want to ask her or anything you want to talk about with her so you don't forget while you are there.
Hope that helps!