
Hi,
I think the best way to tackle this is to treat your youngster as If she were a newly arrived pup! Please don't think I am in any way critiscising what you have tried so far because I really am not but I think your little girl is probably confused and has never really understood that she should not go in the house.She is probably picking up on your anxiety and hence the reason she sneaks off to toilet.Not saying you are chastising her but dogs can always pick up on our emotions even if we don't utter a word.
I would try the following
1) every hour during the day take her outside on a lead to where you want her to toilet.Do not wander around all over but pick just a small area of the garden.(yes every hour I'm afraid)Use a timer to remind you if this helps
2) pick a word such as hurry up and try to say this in an upbeat manner without sounding anxious. Try to avoid too much eye contact if she trys to jump up wanting to play
3)When she does have a wee or poo tell her good girl and give her a treat,something nice and tasty and give her a pat.
4) if after 5 mins she hasn't done wee etc then take her indoors without saying anything and take her lead off and repeat process in an hour.Don't stay out for much longer than this as she will probably switch off and start to want to play or wander around.
5) don't give her free acess all over the house while you are toilet training,either keep her in the room where your husband is or put her in kitchen or a confined area.if she is used to a crate pop her in that when you can't watch her but not for too long a time, or you could use a puppy pen or put a stair gate up to create a small area in say a utility room.
6)ignore any accidents in the house,don't say anything to your dog just clean up with a biological cleaner
7) try to keep a record of when she does actually toilet and you may see a pattern over a few days and try to prempt when she is most likely to need to go,such as first thing in the morning within an hour of a meal or after a nap etc
the most impotant thing is to be consistent,too praise the toileting as soon as she has gone in the desired place,ignore accidents and for a while to accompany the dog into the garden whatever the weather.
the majority of this is going to fall on your husbands shoulders as he is the one in the house with her for most of the day.She is still only a youngster and hopefully will get the hang of things.I equate toilet training a dog to being like potty training a child and by that I mean you have to set aside time for the penny to drop. If after a week she starts to toilet on command when on the lead then you can stop using it but still go outside with her for a few more weeks until she really knows what it is she is outside for and keep on using your desired toilt word.after a few weeks of sucess then she can have more free acess to rooms in the house
hope this helps and I'm sure others will have more tips but I would suggest you pick a method and stick to that one,not necessarily mine,to avoid overloading and causing stress and confusion for yourself and your dog
best of luck