My husband and I collected our 12 week old working bitch 'Wilma' a little over a week ago. She is our first cocker but we have previously had a border collie and springer spaniel. Training is going well generally, but she has become overly dependant on us...particularly myself, to the point where she will whimper if I leave the room or cry if we separate her from us behind a baby gate.
Some progress had been made in the past couple of days. She spent last night in the kitchen (as opposed to crated in our bedroom) with crying gently for only 20 mins, and a brief episode of howling upon waking 2 hrs later. She has her crate open in the kitchen but remains behind the baby gate, effectively providing a puppy pen for her where she can toilet on puppy pads, which she uses well.

The main concern is when we leave the house. If she escalates to loud crying/howling in the house, she quiets quickly after a firm 'no' by retreating to her bed and settling down. But if we are not in to provide this 'no' she continues to escalate. We have tried to gradually build time away from house, but always return to her howling. as we are attached to neighbours and will need to leave her home alone for 3-4hrs a day, we really need to get this under control.

Some things we have tried include: tiring her before leaving (which works if we stay in house and lock her in separate room but doesn't if we leave), feed, water, toilet, stuffed kong toy (only plays with this when in the same room as us), her toys (again, only if we are present), spending time separated during the day to acclimatise to being alone (slow progress made, but again requires a firm no to settle for any length of time), radio on, puppy heartbeat sensor in crate, etc.
We collected her from her mother and brother so she has never been alone until recently. Am I expecting too much too soon? Has anyone had similar experiences, and found that perseverance paid off? Any ideas of what else may help her?

Besides not wanting to annoy the neighbours, I want to ensure we are minimising her distress.
I was aware that cockers 'love people' and company, but want to build her tolerance so this doesn't escalate further. Surely cockers are able to tolerate some time alone??