Yup, don't pull away. The pushing into boob thing is handy if they aren't letting go of their latch - it just gets them to break off quickly, it isn't scary for them.
This link below has a good 'summary' of the main advice.
http://www.kellymom.com/bf/older-baby/biting.htmlThe main thing is timing as a baby can't effectively nurse for milk and bite at the same time so biting occurs at the beginning and end of sessions or on a break. You can normally see a position change in the jaw (and occasionally a baby might look at you with a little twinkle in their eye!. Sam used to 'gum' me pre-teeth and I could definitely tell when he was thinking about it!!!). Keep a little finger ready to break latch quickly.
Some people talk about shouting a firm 'no' but that seems to backfire more often than not - either inducing a nursing strike through fear
OR baby thinks 'Wow! What was that exciting noise and how do I do it again!!'.
If baby is uncomfortable from teething that could account for biting down so consider teething remedies - herbal options or other pain relief. Offer a clean cold wet washcloth to bite down as a substitute.
If teeth are very new it sometimes takes a few days for baby to get used to feeding with them and adjust latch. Don't be shy about breaking latch if it doesn't feel right and readjust.
Hope that helps.
You sound like a useful cousin to have around!!!