Yes, In a very limited sense, the revised version of the character (after her 2001 upgrade) may be able to make very small objects which could retain their existence as long as she thinks about them. She was always able to create small accessories (purses, belts, handbags, hand mirrors, eyeglasses) which augmented her disguises and no one ever thought deeply about it.
I suspect her upgrade was less about making objects and more about turning her into a more malleable and hopefully interesting living weapon. If I were a responsible writer, I would try and keep such transformations into objects into short term events. Or just create a material she could transform in the same fashion as she does her cellular structure.
- Mystique was once limited to changing the appearance of her cellular structure so she could resemble a person's physical makeup and appearance up to and including clothing. She also had perfect pitch and could imitate the sound of a person's voice as well.
- She made her body into the material she needed to appear as. This would let her imitate small detachable objects such as purses, or metallic objects such as zippers or clasps aiding in the authenticity of the objects appearance.
- The problem was her powers were poorly defined and poorly explained. I suspect this had more to do with the character's origin and popularity requiring writers to "make it up as they went along." When you started thinking about HOW the character did what she did, inconsistencies were starting to show up.
This required an analysis of her powers and eventually a correction to their description:
Her cellular structure was far more malleable than believed since she could make metal where our bodies did not have nearly as much metal available at the cellular level.
She was not just transforming her cells, she was transforming matter at a limited level.
She had been seen converting metals from her clothing into weapons. It was not disclosed whether that was a special technology or a power she kept hidden until then.
In 2001's X-Men Forever miniseries, Mystique is exposed to dangerous levels of radiation in order to save the life of Toad. The process morphs Mystique's appearance to match her more reptilian physique from the 2000s film trilogy, and boosts her powers so that she can now morph her body into taking certain desired physical traits depending on her situation at the time.
With her revised powers (a classic Marvel "Radiation Accident") her transformations now include powers such as night vision, wings on her back, talons in her fingers, and natural body armor. These powers make more sense since she would be getting them by imitating things already seen in nature. A cat-like eye would have better night vision, for example.
She can even compress nearly two-dimensional like a sheet of paper to glide on air currents, similar to Mister Fantastic, which she uses to survive an explosion. She has moved her vital organs out of place in order to survive a gunshot to her torso. This is a bit more of a stretch (pardon the pun) but since matter transformation has been shown, the writers decided to go ahead and utilize it in a limited fashion, giving the character more durability and flexibility in combat.
She has, once with strain, given herself two heads and four arms to facilitate a gun fight on two fronts, as well as shapeshifted into herself as a small child. She is also now able to hold a shape when knocked unconscious and can conceal items in shapeshifted pouches under her skin.
- The two heads, four arms thing was overkill (I will attribute it to the 'moment of awesome' trope) but her being able to maintain her shape after being rendered unconscious only makes sense, or she would have surely blown more covers as a double agent over the years. Size changing, we will go with matter transformation again. So many heroes can do it, you should be able to hand-wave it away.
This was clearly the case of a character whose powers were poorly defined and allowed her to do things that were not explained well (where did her clothes come from, how did she take them off, where did the metal in her clothing come from, why didn't she have the power to transform into shapes other than human, why didn't she get any special abilities, etc) and "corrected" during a movie tie-in. This made the character appear physically the same as her movie version and allowed writers to try and clean up and stabilize a power suite that would allow her to keep up with the diverse powers of the X-men.