D.D.
As a licensed early childcare provider for 12+ years and mom to 3 kiddos, I have had my fair share of potty training to say the least :) My suggestion is to continue with the potty training- you'll be so glad you did! My own kids were fully potty trained by 18 months(g), 26 months(b), and 22 months(g), so yes it is very possible that she is ready. So long as she is showing an interest I would certainly carry on. Of course continuing it to keep it fun- can't tell you the number of potty dances and pee-pee celebrations I have taken part in ;)
If she is using a potty chair, I would suggest purchasing the exact same one for you to transport to grandparents/babysitters. You may also want to try her on a nice comfy seat that fits on the toilet- (I always went right to this in order to avoid transitioning from potty chair to toilet seat).
As for underwear, I have always had good luck with the padded training undies w/ the rubber liner. Gerber makes one (http://www.pottytrainingconcepts.com/WMT_AI1G.html). I believe they are available at Walmart. I much prefer "Big Girl" undies rather than pullups when potty training. If she is not yet comfortable with the underwear, you may want to start out by putting them over her diaper/pullup for the first week...just to get her use to the idea. At night, I would call her pullups "night-night undie" or something similar so that she associates them with only being worn at night.
It's a lot of work, but well worth it. If I can help any other way, please don't hesitate to contact me! Good Luck