[Help] Rescue Jack Russell, about a year old - isolation anxiety

Hi all, I've done a bunch of reading on this forum about separation anxiety, but nothing was exactly like what we are seeing with our new jack russell, so I figured i'd post for some specific advice. We just rescued a Jack Russell who had never been away from humans or other dogs for the first year of her life. My wife and I have a staggered workday, so we are gone for roughly 7 hours (8:30 to 3:30) where Lucy is alone in our house. We originally tried crating her for this time, but without being able to slowly introduce her to the crate, she would just spend all day howl and pulling at the cage, to the point where her mouth was raw from pulling. When she was crated while we were home, she was completely calm. The raucous only started when we left.So we decided after about a week of crating to see how she did loose in the house for the day. She still got a bit crazy with the howling when we left, but she's not destructive and she doesn't eliminate in the house. Over the past 2 weeks of this, she's slowly started to remain calm when we leave (with the help of a melatonin treat), but after lunch, in the two or three hours of her isolation, she runs about an howls. Again, nothing destructive, but we feel bad. Do you think we're on the right track, and she's almost got this figured out? is there anything else we can do to help her out in the afternoons? or is this something she just needs to get used to? When we're home, we are always playing with her, walking her, or letting her run around in the backyard, so she gets plenty of activity. She's walked every morning before we leave for the day.Dog walkers in the area are prohibitively expensive ($20-$30/day)thanks Dan via /r/dogs http://ift.tt/2rEYidS