Just keep an eye on her those collars are more useless and traumatizing then any good
As for tumours in dachshund's maybe you can send an email to some doxi rescues and see if they can give you any advise. I'm sure they have lots of experience. Also you can try sending emails to breeders, some don't mind sharing their information. I've done this before with a pointer that I fostered and they were quite willing to help out.
Wish you luck and keep us posted.