"Cephalexin Capsules may be used in the treatment of some respiratory infections, urinary tract infections or skin and soft tissue infections such as wounds, abscesses and lacerations in dogs and cats. Cephalexin is commonly given in a dosage of 10-15 mg per lb body weight every 8-12 hours."
You could try that. It shouldn't harm her so long as you get the dosage and frequency of dosage right. And so long as the medicine has been stored properly (cool dark-ish place) and isn't out of date.
It is really important that you find a plan from here on, for any medical care your dog might need. It's obvious you really love your dog, but they are like us, and can need medical help without warning. Some things have to be seen by a vet.
(This really should....but the cephalexin may help. But what would you do if it didn't? Or if there were side effects? Or if she were allergic?)
The nipple leakage might be caused by hormonal upset. Has she been spayed? If not, such things are fairly common and often present as a symptom of "false pregnancy". If she has been spayed, then there might be more of an issue which could need further investigation.
If she is pregnant...you didn't say....then that is a completely different issue. So would it be if she'd just had a litter of pups. AND I am unsure how safe it would be for the pups to give any medicine including an antibiotic, to a nursing mother....All those questions could be answered by a vet you see.
I once compiled a list of financial resources here on Dogs MedHelp for anyone who cannot afford vet's fees. (U.S. list only)
Here is the link:
https://
www.medhelp.org/posts/Dogs/Financial-Help-for-pet-owners-USA-only/show/2911614#post_13963788
I don't know if everything there is current. I posted that in 2016. But I hope you might find some help there.