Because she's so large, and not knowing your physical limitations, I can only suggest a sling for her hips. Something that you slip under her belly, that you can lift up on, to take some of the strain off her hips. You'll still have to walk up the ramp with her (which may be an issue unto itself), but it would make things a bit easier on her.
You can try it with a towel or pillow case folded up lenght-wise, to that it's about 4-6" wide, and if it works, maybe get something that you can have a handle on, to make it easier for you.
There is a lot to be said for having 5# dogs :B....even 8 of them!!:B