This question may be difficult, since relations between daughter-in-law and mother-in-law are often very difficult. But mother-in-law is a woman. Therefore, a gift should be as usual for women.
And even competent and with the soul, the chosen gift can reduce all the disagreements between the mother-in-law and the daughter-in-law on no and establish their relationship. If this, of course, is a goal. Therefore, refer to the choice of such a gift should be seriously and responsible.
You can go along the path of least resistance: to give the mother-in-law a set of bed linen, a beautiful vase, an expensive service, a double boiler, or something else from home appliances. A good gift can be jewelry, if the mother-in-law is not indifferent.
Flowers will not be superfluous. Like an envelope with money, if the choice of a gift is difficult for you.
You can choose other gifts. The main thing is to have a particle of your soul …