[cypher]

She could be allergic but I wouldn't expect one bald spot from that, you'd more likely see itching & or respiratory problems, try & find her another house she'll like if you can as that could be causing it if she has to squeeze in.
Any holes or entrances should always be big enough to get through comfortably, if they're too small there's always the potential for them to get stuck which is both stressful & dangerous.