For a Homeopathic remedy, a lot more information is needed.

First thing I'd think of is allergy - could be to anything, either in house or out and very possibly started by vaccine reaction.

I'd feed real fresh food - preferably organic, spring water, use no chemicals in house for washing clothes, cleaning or anything, not put chemicals in her body ie worm and flea treatments as they can be done naturally and consider giving her nettles for a while as they can help with allergies. Lots of fresh air and exercise.

If she's stressed by the new pup, consider Flower Essences too.