To find the total grade points for Tessa's first three semesters, we use the formula:
\[
\text{Total Grade Points} = \text{Cumulative GPA} \times \text{Course Units}
\]
Substituting the given values:
\[
\text{Total Grade Points for 3 Semesters} = 3.18 \times 46 = 146.28
\]
For the fourth semester, we calculate the total grade points similarly:
\[
\text{Total Grade Points for 4th Semester} = \text{GPA} \times \text{Course Units}
\]
Substituting the values:
\[
\text{Total Grade Points for 4th Semester} = 3.74 \times 12 = 44.88
\]
Now, we sum the total grade points from all semesters:
\[
\text{Total Grade Points for All Semesters} = \text{Total Grade Points for 3 Semesters} + \text{Total Grade Points for 4th Semester}
\]
Calculating this gives:
\[
\text{Total Grade Points for All Semesters} = 146.28 + 44.88 = 191.16
\]
Next, we find the total course units:
\[
\text{Total Course Units for All Semesters} = \text{Course Units for 3 Semesters} + \text{Course Units for 4th Semester}
\]
Substituting the values:
\[
\text{Total Course Units for All Semesters} = 46 + 12 = 58
\]
Finally, we calculate the cumulative GPA using the formula:
\[
\text{Cumulative GPA} = \frac{\text{Total Grade Points for All Semesters}}{\text{Total Course Units for All Semesters}}
\]
Substituting the values:
\[
\text{Cumulative GPA} = \frac{191.16}{58} \approx 3.295862068965517
\]
Rounding this to the nearest hundredth gives:
\[
\text{Cumulative GPA (rounded)} = 3.30
\]
The cumulative GPA for Tessa over all four semesters is
\(\boxed{3.30}\)