No spell will permanently make the two of you last. A binding will keep you together, even if you break up again you will keep bumping into each other possibly until the day you die. But a binding won't make her love you. There are love spells you could cast, but those too aren't permanent, you're forcing your desire over your ex, overpowering their choice. Your ex will Keep fighting against the spell subconsciously, once they break it, they will leave you, so you would have to recast often.
If I were you I'd make a honey jar so your ex will soften to you again then ask to talk. If you can't work things out, while painful, you should let them go.