Step 1: Note the extremes.
The longest time is $8$ years and the shortest is $3$ years.
Step 2: Read clue (L).
Rhea took more time than only Amrita and finished in $5$ years; so Amrita took the least, $3$ years.
Step 3: Fix Amrita and Rhea.
Amrita $=3$ and Rhea $=5$, and everyone except Amrita took longer than Rhea.
Step 4: Place Smita and Deepa above Rhea.
Both Smita and Deepa took more than $5$ years, and one of them is the $8$-year maximum.
Step 5: Read clue (M).
Smita did not take longer than Deepa, so Smita $<$ Deepa, making Deepa the $8$-year maximum.
Step 6: Order minimum to maximum.
Amrita, Rhea, Smita, Deepa.
\[ \boxed{\text{Amrita} \rightarrow \text{Rhea} \rightarrow \text{Smita} \rightarrow \text{Deepa}} \]