if she can do it on her own, chances are she'll be fine. don't stress yourself out too much about it. against all societal advice, we ended up stomach sleeping our daughter starting at 12 weeks b/c she still startled and woke herlself up. our peditrician actually agreed with us on this as she seemed to do really well. as a result, she had a lot of upper body strength, started crawling earlier, loved tummy time and was able to soothe herself back to sleep.
if you're really worried (and trust me, we were!), you can get a monitor (angel care?) that actually goes under the matress and senses the lack of breath motion... if your baby stops breathing for more than 20 seconds, an alarm goes off. we found that the sound monitor with it sucked and used it for the alarm only. it took a lot of stress off of me!
if you go that route, keep in mind that your baby needs to be on top of the monitor square under the matress for it to work, so once your baby starts moving around more and more, you'll start to get false alarms. we stopped using it around 6 months after 3 nights in a row of the alarm going off, my running to my daughter's room only to find her sleeping at the top of her bed!
good luck!