Yeah, couch-sharing with your baby isn't very safe, unfortunately. Have you tried putting your DH on the couch and you guys use the bed? Do you have a cot you could take the side off it and push it up against the bed. You may have to fiddle with the height settings and have something firm to fill the 'gap'. It gives you a bit more room to co-sleep together and she can be on the side next to you, rather than in between you both.