I'm sorry for you and your DD...and the other teammates, jealousy just plain sucks!
To answer your questions, "What would I do"...well I'd do both of the options you presented - avoid them and make small talk, when you have to.
It will be much easier on your than on your DD as you can just drop and pick up, sit away from the jealous gymmies parents at meets, and if you find yourself standing next to them a nod and smile is more than enough to remain polite.
It's so tough but I'd encourage your DD to just ignore any negativity from them. If it continues or gets worse I think a talk with the HC should be in order. As time goes on it is likely to pass and it will just be another bump in the road of life that your DD will look back on that made her stronger.
I've seen this at our own gym and found that the jealous gymmie was under enormous pressure at home so she ended up letting it out on her teammates. I'd also remind her to remain nice and polite but take the high road and avoid engaging with her when she tries to talk negative, bring her down, and act jealous