Botox injections relax the muscles in which it is injected. It can be used to lower the arch in brows, or to lift brows. It can be used to alter the shape of the brow slightly, but it would most likely not be a drastic change. A few units injected just above the arch would cause the arch to sit a little lower.
It seems like some of the toxin was either injected or migrated into one of the muscles that lift the corner of the mouth/cheek. This can happen on occasion, but the effects will usually dwindle and disappear within a few weeks to months. Hope this helps!
Botox injections are localized, and different from other injectable medications that are systemic (go into your entire body). In small amounts, Botox injections are safe and effective for relaxing muscles.