Rabbits ears get warm or hot due to their body trying to cool down in warm or hot environmental conditions, or from running around and getting too hot., as they have blood vessels in their ears and this is a normal cooling mechanism for them. In most instances it's not an indication of a fever and infection, especially when the rabbit is behaving normally otherwise. If your rabbits ears are very hot and not just warm, your rabbit may be getting overheated, especially if there is an increased respiratory rate. If your bunny is getting overheated, providing cool tiles to lay on or a frozen water bottle to lay next to, can help. Also if you have air conditioning, that is the most help in keeping a rabbit cool in warm weather.
Some rabbits will contentedly chatter or tooth purr while they are relaxed and not being petted. This is normal behavior from a contented happy rabbit. Tooth grinding from pain is a louder harsher sound, and a rabbits behavior will also be different. They may be hunched in a corner, frequently and quickly changing positions, and displaying other behaviors that may not be normal for them and may be indications of pain. If your bun is behaving normally then it sounds like she is just fine. Rabbits that are sick will usually stop eating and will not behave normally.