Can botox really help with cystitis?

Not directly. Not if u have normal bladder function, there is no reason why it should and would be contraindicated. Botox is injected via a cystoscope which like Botox itself is not advisable in presence of cystitis. It can might help patients with neurogenic bladder dysfunction to facilitate bladder emptying and thus risk of utis or speed up recovery after a uti.
May. Some women did repond favorably to this currently unapproved treatment (fda has not approved the use of Botox for interstitial cystitis). Be aware of significant side effects as well.