My small dog has been shaking and puking white foam?

its my moms dog and it has been acting strangely for the past 6 days sometimes (not always) she will start to shake usually in the mornings or at night it has been a little cool lately so im kinda thinking of ruling the shaking out, but she hasn't been eating very much at all and Ive noticed she sometimes throws up some white foam then whatever she has eaten comes after the first foamy puke. there is no blood only grass and food. she has been acting a little more tired but not to different she still goes outside and chases/wrestles with my dog. my mom is getting kinda worried though. oh and btw "Take it to the vet" is NOT a help full answer don't you think we already thought of that...plus Im just asking this to see if anyone has information on this in case it happened to their own dog or they might have an idea of what is wrong.