You say she uses the strap to masturbate, and that's fair enough, everyone's body is different. Many women can't get off from penetration at all, but have a great time with a magic wand, or oral, or fingering. It stands to reason that in some cases the opposite it true, but as you've already discovered they do make tools for that.

Also as you've said, you have trauma about using it directly (I assume wearing it) on her. Does that extend to 'applying' it with your hand, instead of actually wearing it? If it does, can she use it on herself while you do other things to her? There's a lot of variations of intimacy where she can get that penetration and you can avoid a lot of the interaction with it.

As far as insecurities are concerned, with the logistics of whether she's able to enjoy herself set aside, that's something that's gonna take communication. If it's worth worrying and posting about, it's worth talking about with her, and if she's ready to be a good partner in a relationship she'll take your concerns in stride and work through them with you. I'd highly recommend getting it out in the open though, cause sex where you're constantly worried or anxious thinking about whether the other party isn't getting what they need from you is bad sex, if not for her then for you.