Hello, I'm Dr. Deb and will do my best to help you today.
I'm sorry that the bacon didn't agree with your dog but gastrointestinal signs are often ones which can be seen after dietary indiscretion of this sort.
I'm glad that she's no longer experiencing any gastrointestinal signs but I can understand why she might seem a little lethargic today. The loss of electrolytes from her gi issues could easily cause it.
I'm not certain that an ER visit is necessary, not just yet anyway. I might treat her as outlined below to see if she's going to start behaving like her normal self:
1. I'd wait for 8-12 hours after her last bout of vomiting before feeding her. Then, rather than her regular diet, I'd feed her a small amount of 1 part boiled, skinless, boneless chicken breast to 4 parts of 20-minute white rice, 3-4 times a day.
2. I'd let her drink only a small amount of water at one time if it's been a few hours since she last vomited. Pedialyte is an excellent option in this situation since it can help to replace electrolytes which she may have lost.
3. Over the counter Pepcid AC (Famotidine) can be given which may help with any residual nausea issues. The dose would be 10 mg twice a day for a dog her size.
More than likely, she'll be just fine if her gi issues were related to the bacon she ate (which makes sense); however, if she continues to remain lethargic and/or she doesn't want to eat and/or her gi issues return, then a vet visit may be prudent.
I hope this helps and that she's back to normal soon. Deb