Went thru this with Johann.
Can you scrunch the tunnel up so it is really short? Mine is really long when extended, but can be shortened to about 3 inches wide for storage.
I kept it like that and click/treat for every time Johann looked at it. Then I put a treat right in front of it (click/treat) for a few nights. Then the treat was inside the fabric (click/treat) for a few nights. Then I put the cookie on the other side so he had to stick his head thru (click/treat). Then gradually moved the treat so his front legs were thru the tunnel, then half his body, and finally his back legs. We spent a lot of nights with DH holding the tunnel and me throwing treats through it for Johann (blocked off around it so he had to go thru to get the treat). This whole process took about 2 weeks, don't move up until your dog is 100% comfortable with the previous step.
Then I borrowed a very short tunnel (2-3 ft?) long tunnel from my trainer. Repeated the entire process above, although it took much less time (was running thru it the first night).
Once he would go thru the short tunnel with no lure, I set up the full length one again.
He was more comfortable, but I had to crawl thru it first and he followed me.
After the first time (I think he thought he'd get in there and never get out again), Johann has been a tunnel loving fool. Literally tries to run thru it as I'm setting it up each spring. He incorporates it into his backyard boxer burns on a regular basis now.
The training takes a long time, but you definitely don't want to force her thru it (tried it, didn't work). Keep working on it.