I don't think masturbating is being disrespectful, but it does seem a little insulting that you hide it from her. I know you know she'll feel guilty, but she'll probably feel worse if she catches you and realises you've been trying so hard to keep it from her. I'd say talk to her about it, say that you do have urges and are happy to satisfy them yourself with no pressure or demands on her, and once it's all out in the open, then you can do it 'opnely' - not sneaking around like a porn-ninja, but not rubbing it in her face either - and she can either acknowledge it or not as she feels. There's always a chance that she knows you want it, and is feeling guilty as it is thinking you're abstaining (or worse, is getting paranoid that you are or will seek satisfaction elsewhere!). If she knows that you're taking care of yourself in an acceptable way, and aren't expecting anything from her, but are giving her the option of talking about it if she needs to, then while she might feel guilty initially, she can relax more after that knowing that there's no need to worry about it.