I was in a similar situation to you OP.
Also inb4 someone calls me.a fag, yes I am. And I'm happy.
I'm currently dating an absolutely beautiful femboy. Sweetest soul I have ever known. He makes me happy and fulfilled, he has the same interests I have, loves food and I love cooking nice meals for him, accepts that I'm kinda autistic and helps me through my anxieties, merely spending time with him brings me peace, princessy feet with the softest soles ever and adores getting pedicures and painting his nails, indulges in all my kinks enthusiastically simply because I love them.
He just LOOKS so ticklish, anon. Pic 100% related (he literally looks like an irl hispanic version of the character in the pic).
But guess what. He isn't insanely ticklish. God made him a lee but forgot to make him sensitive. The first time I took off his shoes and socks in my car and raked my nails over his soles I got...nothing. My heart sank.
Now, this is where you have to make a decision anon. Does the fact that your girl also isn't ticklish outweigh everything else? Does she make.you happy? Does she give you peace. Because let me tell you anon, when you find someone like that in this chaotic, messy world, you hold on. Because people like that don't come into our lives often.
What me and my boyfriend did to satisfy my tickling fetish is that he lers for me.instead. Turns out I (the fit, hairy guy with a full beard and deep ass voice) am insanely ticklish, and when he ties me up and blindfolds me he wrecks my shit super easily. And those long, manicured nails of his? Pure hell, especially on my feet. And he is a very enthusiastic ler and has wayyyy too much fun making me his bitch.
So tickling is still very much a part of our sex life together, just in a way I did not think it would be. Maybe your girl can do the same to you? If you're a switch of course.
If you are fully a ler, then don't lose hope either. My boyfriend turned out to also be devastatingly ticklish, just in some unconventional ways. His feet are immune to nails, I even oiled up his soles and hairbrushed the shit out of them and he didnt even flinch. But super fast and hard gnawing on his soles (idk why this and not the hairbrush, the human body is fascinating) drives him bonkers with laughter. And don't get me started on his ears, poor thing freaks out and dies when I pin him to the bed and sloppily lick those.
Soo maybe your girl is resistant to most conventional tickle methods, but has some secret weaknesses you just havent found yet. Don't give up hope anon.
Relationships need to be cultivated and worked on for them to work out. They are like a flower, you need to water it or it'll wither away.