Winnie's ears didn't stay up until he was about 19 weeks old. I tried taping them but that lasted about 5 seconds. I would just leave it up to nature. It probably just means her ears will be on the larger side.
I thought Bonnie's ears would never stand up! They were 'up' when I got her at 17 weeks, and went down immediately there after. Didn't go back up until she was 5/and a half months old! They have stayed up.
I believe it may be due to teething as a previous poster had stated. I recall them actually standing up before she started her teething phase and then them starting to flop some. Now both her ears are flopping over compared to my profile pic where one ear is standing up. How long do chi pups teethe btw? And is there anything I can do to help with her teething like specific toys or treats?